researches on malaria - nobelprize.org · 2020-02-05 · researches on malaria 29 which cause...

RO N A L D R o s s

Researches on malaria

Nobel Lecture, December, 12, 1902*

Contents1. Preliminary p. 26

2. The discovery of the parasite of malaria p. 273. The problem of the mode of infection p. 294. First researches in India; 1889-1894 p. 30

5. Return to England; 1894 p. 316. The theories of King, Laveran, Koch and Manson p. 32

7. Nature of proposed investigations p. 368. Preliminary observations at Secunderabad; 1895 p. 37

9. Secunderabad; 1895. The motile filaments in mosquitos p. 3810. Difficulty of the task. The methods devised p. 3911. Bangalore; 1895-1897. Progress of work p. 42

12. The Sigur Ghat; 1897 p. 4913. Secunderabad; 1897. The fundamental discovery p. 5314. Interruption; September 1897-February 1898 p. 62

15. Calcutta; February-April 1898. The theory proved p. 6516. The Darjeeling Terai; April-June 1898. Efforts to obtain assistance p. 72

17. Calcutta; June-August 1898. The route of infection p. 7618. Darjeeling District; August-September 1898. Kala-Dukh p. 82

19. Assam; September-November 1898. Kala-Azar p. 8320. Calcutta; November 1898-February 1899. The work confirmed p. 85

21. England; March-July 1899. Foundation of the Liverpool Schoolof Tropical Medicine p. 89

22. Sierra Leone; August-September 1899. The investigation completed p. 9223. Confirmation and extensions p. 94

(1) The work of Koch p. 94(2) The Italian writings p. 96

(3) The Commission of the Royal Society p. 103References p. 105

Plates p. 110

* The lecture as given on this occasion was only an abstract of the present publication.

26 1 9 0 2 R . R O S S

1. Preliminary. Malarial Fever, or, as it is often called, Paludism or IntermittentFever, is perhaps the most important of all diseases which afflict humanity.Broadly speaking it is spread over almost the whole of the tropics, and also ex-tends into many countries which possess temperate climates - being found asfar north as Sweden and Canada. Although, happily, it is not a very fatal dis-ease, yet it is generally so prevalent in the countries in which it exists that thesum of the illness which it causes is immense. To take for instance the greatcountry of India with its enormous population of nearly three hundred mil-lions, we find from the sanitary returns of the government that the deaths fromfever alone are given at 4,919,591 for the single year 1900; and average roughlyabout five million deaths yearly - a population nearly as large as that of Swe-den and Norway. Although it is not possible to state that all this fever is mala-rial fever, there are reasons for thinking that most of it must be such. From themore exact returns of the army and of the jail prisoners in India - returns at-tested by medical men - we find that in 1900, out of the total of 305,927 per-sons, no less than 102,640 were admitted into hospital for malarial fever duringthe year; and even this large figure is below the truth, because in India manyslight cases of fever are not admitted into hospital at all. The following Table I

taken from the returns of the British Troops in India for 1900 will enable us tocompare the sickness due to malaria and to other diseases respectively.

It should be noted that the death rate for malaria is here far below the truth;because, the disease being often very chronic, many of the worst cases are in-valided to Europe; while in others death is often recorded as being due to inter-

R E S E A R C H E S O N M A L A R I A 27

current affections, such as pneumonia or dysentery, even though malaria mayhave been the original or principal cause of the fatal result.

Similar statistics will be found in most of the tropical countries of the worldwhere statistics are kept at all. Even in such a temperate climate as Italy, theannual number of cases amounts, according to Celli, to something like twomillions, while the number of deaths may be fifteen thousand a year. For thegreat continent of Africa we have, of course, no figures; but we know fromthe important discovery of Koch, confirmed by many German and Britishworkers, that between fifty and a hundred per cent of the negro children al-ways remain infected from which also we may assume that the terrible in-fantile mortality among negroes is largely due to this disease.

But malarial fever is important, not only because of the misery which it in-flicts on mankind, but because of the serious opposition which it has alwaysgiven to the march of civilization in the tropics. Unlike many diseases, it isessentially an endemic, a local, malady; and one which unfortunately hauntsmore especially the fertile, well-watered and luxuriant tracts - precisely thosewhich are of the greatest value to man. There it strikes down, not only theindigenous barbaric population, but, with still greater certainty, the pioneersof civilization, the planter, the trader, the missionary, the soldier. It is there-fore the principal and gigantic ally of barbarism. No wild deserts, no savageraces, no geographical difficulties have proved so inimical to civilization as thisdisease. We may almost say that it has withheld an entire continent from hu-manity - the immense and fertile tracts of Africa; what we call the dark con-tinent should be called the malarious continent; and for centuries the successivewaves of civilization, which have flooded and fertilized Asia, Europe, andAmerica, have broken themselves in vain upon its deadly shores.

2. The discovery of the parasite of malaria. From the first then, the study of thispotent foe of mankind has given a great occupation to science. It is not withinmy province at this moment to detail the early steps by which science grad-ually penetrated the mystery-steps, however, which are not the less interest-ing to follow. Though it was well known to the ancients, the disease was notclearly differentiated from other fevers until much later. Towards the middleof the seventeenth century, however, physicians recognized that in cinchonabark we possess a drug which is a specific for a certain class of fevers, namelythe intermittent fevers. As Kelsch and Kiener remark, this discovery was notonly an immense therapeutical benefit, but also led to a notable pathologicaladvance, because it enabled Morton and Torti to prescribe the exact limits of

28 1 9 0 2 R . R O S S

the disease curable by the medicine, namely malarial fever; and the works ofthese writers, especially Torti, who without possessing thermometer or mi-croscope accurately described the intricate course of the disease, are among themost admirable works of medical science. At the end of the seventeenth andthe beginning of the eighteenth century Morton and Lancisi elaborated an-other important conception, that the disease is produced by some poisonwhich enters the body from without; and the latter especially clearly under-stood what may be called the great law of malarial fever that it is connectedwith stagnant water on the ground. The next great advance was made in themiddle of last century by Meckel, Virchow, Planer, Arnstein, Frerichs, andothers, who discovered that the disease is characterized by the presence in theblood and some tissues of a peculiar black granular substance, the malarialpigment or melanin; and this observation led directly to the great discoveryof Laveran in 1880, that the melanin is produced within multitudes of minuteamoeboid parasites which live within the blood corpuscles of the patient - adiscovery which not only illuminated the whole subject of malaria, but, byopening a new department of parasitic pathology, has put the name of Lave-ran in the place of honour beside those of Pasteur, Lister, and Koch.

The work of Laveran and of those who followed him affords one of themost beautiful and useful chapters in the whole book of science; and I wishthat it were possible to deal with it here at length. We owe to Danilewsky,Theobald Smith and others the discovery of similar parasites in the blood ofmany vertebrates, and to Laveran and Golgi the determination of several important laws concerning the whole group of these organisms. Marchiafava,Celli, Mannaberg, Metchnikoff, Canalis, Antolisei and many others addedimportant details; Kelsch and Bignami made minute clinical and pathologicalstudies; Romanowsky discovered the best method of staining the parasites;Gerhardt and others produced infection by inoculating the blood of patientsinto healthy persons; and Richard, Councilman, Vandyke Carter, Osler,Plehn and numerous other skilled observers confirmed those results in manyparts of the world. The principal conclusions reached by this mass of investiga-tions are as follows :

(1) That Laveran’s parasite is the cause of malarial fever.(2) That it is a sporozoon belonging to a group probably allied to the Coc-

cidiidae, of which other members are found in birds; and that somewhat sim-ilar but more distantly related haemocytozoa are found in other vertebrates.

(3) That the organisms propagate in the blood by spore formation.(4) That there are probably at least three varieties of the human parasites,


which cause respectively the quartan, the tertian, and the irregular (perniciousor aestivo-autumnal) fevers.

(5) That the paroxysm of fever commences with the release of the spores.(6) That with all varieties of the parasites, there are certain forms which do

not produce spores, but which, shortly after blood containing them is drawnfrom the host, emit certain singular motile filaments; and that the nature andfunctions of these forms still required further investigation.

3. The problem of the mode of infection. But even after all these fine discoveries,there still remained for solution a problem of the greatest difficulty and of thegreatest importance. We had discovered the pathogenetic organisms of ma-larial fever, and had studied them and their effect with the greatest care. Thiswas much, but not all; it sufficed for the treatment of individual cases; but notfor the prevention or extirpation of the disease on a large scale. For this wewere obliged to seek a wider knowledge: the parasites occur in the humanblood - but how do they arrive there? On this scientific question turned thewhole prophylaxis of malaria - a subject the importance of which in connec-tion with the future development of many of the richest portions of theworld’s surface I need not enlarge upon. Ignorant of the route of entry, wecould rest our prophylaxis only upon an unsatisfactory empirical basis; cog-nizant of it, we might hope to stamp out the plague even in its most redoubt-able haunts. It is my privilege in this lecture to describe particularly the stepsby which this great problem has at length received its full solution.

In what manner precisely does the malarial infection reach the humanblood? From early times certain cardinal facts regarding the disease have beenknown to us and have limited the area of investigation regarding this question.It has been recognized, first that malarial fever is essentially an endemic disease- that is, that it does not easily spread from man to man independently of local-ity, as do for instance, small-pox or plague; secondly that it adheres especiallyto warm localities where there is much stagnant water, such as marshes. Uponthese facts, themselves perfectly true, numerous hypotheses have been con-structed; notably the one, dating from the times of Lancisi and Morton, thatthe disease is due to miasmata exhaled from the stagnant water whence in-deed the word malaria has originated; and later the allied theory of the telluricmiasm, according to which the soil possesses a poisonous effluent so powerfulat certain spots that it can there produce fever in man. It was even thought thatwhen the surface of the ground is disturbed, this effluent escapes like a gas,infecting all those who live in the vicinity. These speculations afford an in-

30 1 9 0 2 R . R O S S

teresting example of the manner in which the human mind is apt to embroiderfact with hypothesis. It is a fact that malarial fever is connected with stagnantwater; but that the connection is due to an aerial emanation from the stagnantwater was only an hypothesis which has never received experimental verifica-tion. Nevertheless, it was almost universally accepted until the true explana-tion of the connection referred to was given in the manner which I shall pres-ently describe.

The discovery of the pathogenetic organism by Laveran produced but littlechange in our ideas on this point. It was simply thought that the parasitesmust be capable of saprophytic life in stagnant water, and may enter the bodyby the inhalation of watery vapour or by infected drinking water; and, in-deed, efforts to obtain experimental proof of these conceptions were quicklymade, especially by Calandruccio, Marina8, Agenore7, and Celli and Mar-chiafava4, who endeavoured to infect healthy persons by means of waterbrought from notoriously unhealthy sources. The experiments proved, how-ever, entirely negative - somewhat to the surprise of those who were acquaint-ed with them. At the same time parallel enquiries were commenced to ascer-tain the saprophytic stage of the parasites; and Grassi and Feletti found anamoeba (Amoeba guttula) which they thought might be the parasites in theirfree condition10. Their work recalls that of Crudeli and Klebs who, beforeLaveran’s discovery, claimed to have found the cause of malaria in the formof a bacillus which they asserted abounds in the water and soil of malariouslocalities, especially in the lowest stratum of the air, and gives typical inter-mittent fever to rabbits and other animals. All these observations are nowproved to have been unsound.

4. First researches in India (1889-1894). It is, I understand, the principal duty ofthose who are called to the high honour of presenting the lecture of the NobelMedical Prize to give in it an account of their own researches ; and I shall there-fore begin my personal narrative at this point. * I had entered the medical serv-

* More or less brief abstracts of these investigations have already been published54,68, buttheir brevity has only had the result of permitting the genesis of many errors regardingthe real nature of the task. I have therefore thought it best to give in this publication a ful-ler, and indeed almost autobiographical, narrative of the successive events. It is scarcelypossible, except by this means, to present a true picture of the difficulties in the way of re-solving this intricate problem. As so often happens in science, the most important part ofthe investigations really consisted of the initial failures; and I have therefore describedthese negative results in as much detail as is given to the discovery of the pigmented cellsand of the life history of Proteosoma which afterwards gave the fundamental solution of


ice of the government of India in the year 1881; but, although many opportu-nities for studying the malarial problem had been given me, I was not special-ly attracted to it until the year 1889, when I first began to observe many factsat variance with the telluric hypothesis which had been instilled into me dur-ing my curriculum. I noted especially that the disease had a much more limitedand localized prevalence than could be explained on any theory of aerial con-vection; I found that outbreaks often appeared to occur among troops merelyas the result of chill or fatigue; and that in many instances the symptomsaccorded ill with the classical descriptions. These observations provoked inme much dissatisfaction with accepted theories; and gradually led me to thetask of reviewing the whole subject by close analysis. Unfortunately at thattime it was extremely difficult to obtain in India any of the more recent liter-ature on the subject; and even the discovery of Laveran (1880) had scarcelypenetrated there as yet - much less the work of Golgi, Danilewsky, Marchia-fava and Celli. I was therefore forced to rely almost solely on my own observa-tions and thoughts; and at first fell into the mistaken conception, parallel withthat of Broussais, that the disease may be due to intestinal auto-intoxication;and I published some papers supporting this view12-16. In 1892, however,several writers began to ventilate Laveran’s work, but most unfortunately de-scribed, not the parasites of Laveran, but a number of artifacts.* The error wasspeedily detected and exposed 17,18,20,21 ; but naturally led me (and manyothers in India) to doubt the whole discovery. As happened with many others,although in pursuance of these studies I had made a laborious examination ofmalarial blood for some years, I had failed entirely to find the true parasite atall.** Up to the year 1894, therefore, my work, though it gave me an invalu-able training for what was to come, remained in itself quite ineffective.

5. Return to England (1894). In 1894 I obtained furlough to England; and im-mediately on arrival sought the advice of Professor Kanthack. He assured methat I was mistaken in doubting the truth of Laveran’s discovery, and referred

the problem. It should be added that my work was minutely recorded not so much inpublications, as in a long series of letters to Manson, Laveran, and Nuttall, and that ex-tracts from these letters are now about to be published, together with reprints of some ofmy papers.* Vandyke Carter had accurately followed Laveran in Bombay in 1887; but I did notsee his work until 1894.* * As I found subsequently, one reason for this was that I had been working principallywith old aestivo-autumnal infections in which the larger and more obvious parasites(crescents) were scarce.

32 1 9 0 2 R . R O S S

me to Dr. Manson (now Sir Patrick Manson). Manson, to whom the parasitehad been previously demonstrated in England, now in his turn showed it tome; and also made me acquainted with the invaluable and illuminating mon-ographs of Mannaberg, and of Marchiafava and Bignami. I now collected mystudies in the form of an essay (unpublished) in which I discussed the positionof the malarial problem at the time, and which was accorded the Parkes Me-morial Prize for 1895. In November 1894, Manson communicated to me hishypothesis, just formed by him, that the mosquito is the intermediary hostof the malaria parasite, as he had proved it to be of Filaria nocturna. I wasimmediately and powerfully struck with this hypothesis, and at once deter-mined to give it close experimental examination on my return to India. Atthe same time I remembered that the same hypothesis had been mentioned byLaveran, and I told Manson of the fact. It was not until 1899, after the solutionof the problem, that Nuttall informed me of the earlier theories of King andKoch enunciating the same view. Consequently, I have always thought itproper to state that my own work on that part of the malarial problem whichflowed from the mosquito theory was based on the hypothesis of Manson andLaveran. But I do not wish by this admission to underrate those of King andKoch; and I shall now enter upon a short digression in order to examine allthese very interesting hypotheses together.

6. The theories of King, Laveran, Koch, and Manson. As already mentioned, whenthe malaria parasite was discovered everyone who remembered the old tel-luric and miasmatic hypothesis thought that it must live a saprophytic exist-ence in marshes; and up to 1894 Grassi’s Amoeba guttula was looked upon asbeing possibly the free form of the organism in water. Another interpretationof the connection between malarial fever and stagnant water had, however,been noted as early as 1883 in a remarkable paper by King2. He advanced theview that the malarial poison is carried from the marsh to the human beingby the bites of mosquitoes which breed in marshes; and he gave with greatdexterity no less than 19 reasons in favour of this position - reasons based en-tirely on epidemiological considerations such as the frequency of infection inwarm moist climates, in the evening, in the lower stories of houses, etc. Herefers to a previous enunciation of this conjecture in papers by Crawford in1807 and Nott in 1847, now apparently lost; and he quotes Manson’s filaria-mosquito work as a reinforcement of his views; but he is evidently ignorantof Laveran’s discovery, which was then slowly fighting its way into recogni-tion. A fuller account of his excellent paper is given in Nuttall’s history 65,66.


Laveran’s conjecture was first given briefly in 18843, evidently independ-ently of King. Seven years later he mooted the same idea, still very briefly andwithout giving many reasons 11. The similar conjecture of Koch was not pub-lished at all; but in a letter to me he says that the mosquito theory occurredto him during his first visit to India in the winter of 1883-1884, and thatR. Pfeiffer mentioned the matter publicly in 1892 (see Koch’s letter in sec-tion 23).

As already stated Manson did not arrive at his hypothesis until near the endof 1894, when he drew attention to it (after mentioning it to me) in a shortarticle 22. He based it, not upon the epidemiological considerations of King,but upon a very powerful parasitological argument of his own which was asfollows. The work of Laveran, Golgi, Marchiafava, Celli and others had clear-

Fig. 1. Gametocytes producing motile filaments; the tertian parasite (1-3); the quartianparasite (4-6); the aestivo-autumnal parasite (7-12). From Manson’s paper, p. 644.26

34 1 9 0 2 R . R O S S

ly established that the general life-cycle of the parasites within the vertebratehost consists of a process of schizogony or asexual spore formation, by meansof which the organisms proliferate indefinitely in the blood. But in additionto the sporocytes existing for this purpose, all observers from the time of La-veran had observed certain large cells, which, while they were evidently ma-ture as regards size, did not produce spores and appeared to have no functionwithin the body. Laveran showed, however, that a few minutes after bloodcontaining these cells was withdrawn from the circulation they underwent asingular change - that is, they gave issue to a number of long, actively motilefilaments, capable of separating themselves entirely from the parent cell, andprogressing independently among the blood corpuscles. There had alreadybeen a long discussion about these forms. Grassi, followed by Bignami andmany other Italians, considered them to be forms of degeneration, and heldthat the motile filaments were products of a kind of death agony in vitro. Thereason given for this view was that the motile filaments contain no chromatin(which is not true); but in my opinion these observers had not consideredthem with sufficient attention, or they could not have thought them to bedying bodies. On the other hand Laveran, Danilewsky and Mannaberg, whohad studied them closely, came to the opposite conclusion that they constitutein some way the highest stage of the parasite; and Mannaberg even conjectedthat they may be concerned in the passage from the intracorporeal to the ex-tracorporeal stage of the organisms - though he did not indicate the route bywhich he thought the passage was made. Manson’s speculation broke in atthis point. He accepted Mannaberg’s position; and noted also the general lawthat parasites must attain some means of passing (at least by their progeny)from the already-infected individual into a fresh individual; that the parasitesof malaria being contained within the closed cavity of the circulation cannotescape from it except by the intervention of some external agency (e.g. asuctorial insect); that the position as regards these parasites was indeed thesame as that of the filaria embryos which he had shown require the interven-tion of a mosquito to escape from the infected host; and that the epidemio-logical laws of malarial fever suggest a possible connection with the same in-sect. Hence it flashed upon him that the motile filaments mentioned above arereally flagellate spores, which, when the parent cells are ingested by the mos-quito, escape and enter the insect’s tissues, developing in them into some formanalogous to that of the organisms in the human blood.

Manson continued the speculation to a further point, especially in a laterpublication26. It will be remembered by those who have studied his works


that in his original investigations on the development of filaria embryos inmosquitoes he had failed to ascertain that the insects live for more than a fewdays; he had thought that after a single meal of blood the mosquito lays hereggs on the surface of water and dies in the act of doing so. Consequently,when he had traced the development of the embryos to the stage which theyreach in the insect’s thorax he inferred that that was the whole development,and that after the death of the host on the surface of the water the embryosescaped into the latter and finally infected man by the digestive tract.* And henow applied the analogy to the malaria parasites, and thought that, similarly,after the insect’s death, they enter the water and infect man either by drinkingwater, as he assumed for the filariae, or by the old machinery of the aerialmiasma. Thus Manson’s hypothesis suggested a clue only to the departure ofthe parasite from the human host; it did not attempt to define the routeof entry, the exact mode of infection. In these points he admitted that hisspeculation was looser, and research has shown that he was wrong - certainlywith regard to the malarial parasite and probably even with regard to filariae.In another point also he was wrong - the motile filaments are not flagellatespores, as he thought they were. I remember mentioning to him at the timethat they might possibly be of the nature of sperms - an idea which was sug-gested to me by Lewis, who conjectured that his trypanosoma might be ofthat nature6. We shall see later what they really are. But these errors wereimmaterial. The fundamental part of his hypothesis was the close and power-ful argument to the effect that the motile filaments and the parent cells fromwhich they spring must be meant to infect the mosquito in some manner. Thiswas more than a hypothesis; it was a great and illuminating induction. It gavethe required clue to further research; and without it I am convinced the ma-laria problem would not have been solved at all and we should still be engagedin a laborious and hopeless search for the parasites in water and air.

Cogent as Manson’s arguments appeared to me, they were far from con-vincing to most other students of malaria; and in fact no one else took thetrouble to investigate the matter in spite of its immense importance to hu-manity. In 1896 indeed, Bignami wrote a long and dexterous article attackingthe whole induction29. He still refused to believe that the motile filamentswere anything but the result of death in vitro, and added that if the inductionwere true, malarial fever could be propagated by patients living in the pres-ence of mosquitoes - which he refused to consider possible. At the same timehe evolved a theory of his own to the effect that mosquitoes become infected* Or possibly "by piercing the integuments".

36 1 9 0 2 R . R O S S

with the parasites when in the larval stage in water, and then inoculate theminto man during puncture. Thus while Manson thought mosquitoes carry theparasite from man to the marsh, Bignami thought that they carry it from themarsh to the man. The latter view does not appear to me a very philosophicalone, since it presupposes the possibility of organisms living normally partly asaprophytic and partly a parasitic existence in the mosquito, and then beingsuddenly transferable on exceptional occasions to man. Bignami’s theory,however, was exactly that of King given much more forcibly thirteen yearsearlier. He mentioned that he had previously attempted to infect men by gnatsbrought from malarious localities, but that the attempts had failed. He alsoreferred to experiments made by Calandruccio, who had failed to observeany development of the parasites in the stomach of mosquitoes fed on malarialblood. Lastly he cites another most valuable analogy in favour of the mos-quito theory of malaria, namely that of the Pyrosoma bigeminum, a parasite ofcattle allied to the parasites of malaria, and known by the brilliant researches ofTheobald Smith and Kilborne to be carried by ticks19. Koch also had used thisanalogy, but I think that both Manson and myself had overlooked it some-what unduly.* Curiously enough all this time it seems to have occurred to noone that the mosquito may act in both roles imagined by King and Mansonseverally - that it may both take the parasite from the patient and also inocu-late it into healthy persons. I traversed Bignami’s criticisms in an article whichwill be referred to later (section 11).

In considering the merits of these various hypotheses we must always re-member that all of them have found no little support from Manson’s originaldiscovery of the development of Filaria bancrofti in mosquitoes.

7. Nature of proposed investigation. We must now return to my own labours.As already mentioned, directly I became acquainted with Manson’s induc-tion, I determined to continue my investigation of the malaria problem en-tirely on this new basis.

Before my departure for India I discussed with Manson the best method of

* The development of the Pyrosoma in ticks is still unknown, though the second host haslong been recognized. It should be understood that the history of this organism, and ofthe filaria in mosquitoes, while adding great force to the mosquito theory of malaria, gaveus no information regarding the form and position of the malaria parasites in mosquitoes,nor of the species of insect concerned. The Pyrosoma is not very nearly related to the ma-laria parasites, and the filaria not at all. I was not aware of the work of Smith and Kilborneuntil much later.


procedure.* We agreed that the proper course would be to select patientswhose blood was rich in gametocytes (the name now given to those forms ofthe parasite of which some produce motile filaments); to allow mosquitoes tobite these patients; and to attempt to trace in the tissues of these insects thedevelopment of the said motile filaments (which we thought were flagellatespores). In fact it was proposed that I should adopt exactly the procedure em-ployed by Manson in regard to Filaria bancrofti. It seemed necessary only tofollow the motile filaments, after their escape from the gametocytes containedin the ingested blood in the mosquito’s stomach, to their supposed destinationwithin some kind of cells of the insect’s tissues (e.g. the stomach or blood cells)- apparently an easy task. It was true we anticipated, on the analogy of thefilaria, that not all species of mosquitoes would be amenable to the malarialinfection, and we recognized that this doubt would increase the difficulties;but we hoped readily to distinguish the proper species by its particular preva-lence in very malarious localities. The motile filaments being traced to theirhabitat in particular cells of the insect, we thought that it would be easy toobserve their further development, and to watch their escape into water afterthe host’s death. This done we should be able to identify the extra corporealform of the parasites in water, air, or dew, and to ascertain exactly the routeof infection of man.

8. Preliminary observations at Secunderabad (1895). I reached India in 1895 andfound myself appointed medical officer of a regiment of native soldiers sta-tioned at Secunderabad and suffering much from malarial fever. A survey wasimmediately made of the malarial parasites existing among these men and Ifound myself able to confirm for India, in almost every detail, the specializedwork of the Italians and of Mannaberg.**

* We thought that Manson himself could not undertake the work in England, but thisperhaps would not have been as difficult as we supposed. The parasites have now beencultivated in the local Anopheles at Hamburg and have been found in them in Holland.Work might easily have been done in this direction at home, while I was labouring in In-dia. At all events I should have been greatly assisted by a study of British gnats.** My regiment was stationed near a small marsh and suffered badly, while another regi-ment situated only a mile to leeward of the same marsh escaped. My regiment sufferedfrom the aestivo-autumnal and tertian varieties of parasite, quartan being quite absent;but in the neighbouring regiments of this great garrison quartan abounded - a fact whichconfirmed me in favour of the view that these varieties are distinct and not interchange-able forms. The work of Crombie and myselfwas the first done in India on this basis, thatof Vandyke Carter (1887) being done on the basis of Laveran’s works.

38 1 9 0 2 R . R O S S

At the same time I examined the mosquitoes which abounded in the bar-racks and hospital. Before leaving England I had made many attempts to ob-tain literature on mosquitoes, especially the Indian ones, but without successexcept for some brief notes in encyclopedias; and I did not even clearlyrecognize the identity of mosquitoes and gnats, but thought that the for-mer constituted a special division of the Culicidae.* Consequently I wasforced to rely entirely on my own observations; and I noted that the variousspecies of mosquitoes of the locality belonged apparently to two differentgroups, separated by many traits, and called these groups for my own con-venience, brindled mosquitoes and grey mosquitoes. It was not until 1897 that Iclearly recognized a third group which I called spotted-winged mosquitoes (seesections 12 and 13).

As the grey and brindled mosquitoes abounded round the infected barracks,it was naturally thought likely that they were concerned in the propagationof the disease. After some initial difficulties I caused numbers of them (espe-cially the brindled mosquitoes) to be fed on persons with the gametocytes ofaestivo-autumnal fever (crescents) in their blood. It should be noted that fromthe first I employed for this purpose only mosquitoes bred in captivity fromthe larvae, and not insects caught at random in the houses. There were twoexcellent reasons for this; first, that the insects caught at random might havealready fed themselves previously and have thus, for all I knew, acquired va-rious parasites which might confuse my results; and, secondly, because it iseasier to obtain the insects in numbers by collecting their larvae and keepingthem in vessels until they hatch out from the pupae, rather than by catchingeach separately by hand. The mosquitoes were fed by being released from thebreeding-jar into a mosquito-net within which the patient was placed, thegorged insects being subsequently caught in bottles and dissected as required.

From the first I kept careful notes of my observations, and also recordedthem in letters to Manson sent by almost every weekly mail, except whenlater, being very busy at Bangalore, I was obliged to reduce both notes andletters. The note-books and letters are still in my hands.

9. Secunderabad (1895). The motile filaments in mosquitoes. The first point re-quiring study was the process by which the motile filaments escape from theparent cells (gametocytes) within the stomach cavity of the mosquitoes. Theprocess had been frequently watched in vitro (in slides of liquid blood pre-* In spite of repeated attempts to obtain such literature I remained in the same predica-ment until I returned to England in 1899.


pared for the microscope), and was known to occur in from about 10 to 30minutes after the blood is drawn from the patient; but it was now necessaryto follow it in the mosquito. The insects were killed from one minute to sev-eral hours after feeding, the stomach being then extracted and its contents ex-amined in the fresh state. I was obliged to invent the technique for myself; andmy first successful dissection was made on the 13th May. Within a few weeksI made a fairly complete study of the subject and ascertained an encouragingfact. In vitro, doubtless owing to the unnatural conditions, only about five percent of the crescents give issue to the motile filaments; but I now found thatin the mosquito’s stomach something like sixty per cent of them do so. It wasalso noted that the preliminary stages of the process, namely the swelling upand rounding of the crescents, were much more constantly seen in the bloodingested by the insect than in vitro. This was of importance because it showedat least that the insect’s stomach is a more favourable locus for the process thanan ordinary specimen of blood is. I observed also that a considerable percent-age of the crescents (about one-third) never produced motile filaments at all,*even after the lapse of several hours and within the insects; and I noticed thatthose which refused to emit them had a slightly different appearance to theothers. At the time I thought that they were parasites which had been killedin some manner during ingestion; but when I repeated the experiments nextyear I saw cause to doubt this, and felt some difficulty in explaining why allthe crescents did not emit filaments as they should have done according toManson’s hypothesis regarding their nature.

A description of these first results was written in June, but was not publisheduntil the end of the year24.

10. Difficulty of the task. New methods devised. The fact, then, was establishedthat the gametocytes are not immediately killed in the mosquito’s stomach(as might well have happened), but indeed emit their motile filaments morereadily there than in vitro. It was necessary now to seek the destination of thelatter in the insect’s tissues; and here the true magnitude of the task to whichI had set myself became manifest. Manson had been able to follow the migra-tions of the filaria embryos with comparative ease because they are large or-ganisms readily distinguishable from the fluids or tissues which surroundthem. But the motile filaments are exceedingly delicate bodies, the move-ments of which are very difficult to follow even with the highest powers of a* It was easy to distinguish those which had produced the filaments by their collapsedcondition afterwards.

40 1 9 0 2 R . R O S S

good microscope and in the clear spaces of an ordinary preparation of blood.But the blood in a mosquito’s stomach shortly becomes a thick grumous massin which it is impossible even to see the filaments unless they are in activemovement. Moreover, even this assistance was denied me; for I speedily ascer-tained that within a few minutes of their escape they seemed to lose theirmovements. At least they constantly disappeared as if by magic; and in spiteof all artifices I failed to ascertain what had become of them.* In fact to tracethem further, to follow the migrations of these well-nigh invisible bodiesthrough the masses of cells of which so large an animal as a mosquito is com-posed was indeed an impossible task with the means which I possessed.

Hence, though Manson then and later constantly advised me in his letters toadhere to the plan of following the motile filaments, I determined to abandonthe quest and to emply other methods; and he himself failed to obtain anyresults with the insects which I sent to him from time to time. It was mostfortunate that I came to this decision so early, because events have proved thatthe motile filaments migrate nowhere, and do not enter the mosquito’s tissuesat all.

The first method which I now adopted and which ultimately led to successwas the following. By hypothesis, the motile filaments after reaching the par-ticular cells of the mosquito for which we thought they were destined, shouldgrow in them into some unknown but larger form. It was impossible to pre-dict what this form would be. Manson conjectured that it would very likelybe some intracellular form similar to the intracorpuscular stages of the organ-ism in the human blood - fixed perhaps in the stomach cells or blood cells ofthe insect. Personally, however, while I thought this view possible, I had nofull faith in it. It seemed to me that the mosquito stage of the parasite mightbe anything, so long as it was of a protozoal character.

The protean changes of many of the parasitic worms warned us that naturewas capable of ordering any extraordinary transformations in the interest ofparasites; and as no case was yet known of a protozoon capable of wanderingfrom one species of host to another, I had no guide as to what might happenwith the organisms which I was studyin g, and conjectured that for all wecould say, the motile filaments might develop into almost any form - amoe-boid, coccidiform, gregarinoid, or even infusorial, small or large. What wasnearly certain, however, was that they were likely to grow in size after a few* It might now be possible, though still difficult, to follow them by staining them eitherin dehaemoglobinized blood or in section; but the Romanowsky reaction was not knownto me at that time.


days’ residence in the mosquito - to become more visible, and, if they were topass into the water as we thought they would do, to take a definite form ofresistance which ought to be easily recognizable. My new method then was togive up the attempt to follow the newly escaped and almost invisible motilefilaments, and to dissect the mosquitoes, not at once, but after the lapse ofsome days, during which time the motile filaments should by hypothesis de-velop into something more tangible. I proposed then to feed the mosquitoesas before on cases with crescents in the blood; to keep them alive for somedays; and then search their tissues for any parasites which might occur in them.The parasites found, it would be easy to determine whether or not they arederived from the motile filaments, simply by ascertaining whether or not theyalso occur in mosquitoes of the same kind fed on healthy blood. Throughoutthe investigation it was of course necessary to employ only what I called inbacteriological parlance "sterile mosquitoes", that is mosquitoes freshly hatch-ed from the larvae in captivity and therefore not contaminated by previousfeedings.

Such was the procedure now adopted; but the difficulties involved even init were very great. As the situation of the sought-for parasites could not beindicated with any certainty, it became necessary to search for them throughall the tissues of each insect examined - to scrutinize by a powerful micro-scope, one by one, all the minute cells composing the huge aggregate of whichthe insect consists.* To investigate a single insect thoroughly in this mannerrequired at least two hours’ exhausting and blinding work. Added to this dif-ficulty, I had no clue as to the form and appearance of the object which I wasseeking for; nor was I even sure that the kind of insect under examination wasamenable to the infection at all. I was looking for a thing of which I did notknow the appearance in a medium which I did not know contained it. In shortit was a mere blind groping for some clue which I trusted fortune would givein the end. As an instance of the difficulty of such work I may mention thatneither the organisms of yellow fever, which is now known to exist in a par-ticular kind of mosquito, nor the Pyrosoma of Texas cattle-fever, which isknown to exist in a tick, have yet been found in these animals, though longsearched for by competent observers. Nevertheless, I am confident that, hope-less as the method may appear, it was the only one capable of solving thisdifficult problem.

At the outset of the investigation it was necessary for me to become thor-oughly acquainted with the normal histology of the mosquito - for which I* Under a magnification of a thousand diameters a mosquito appears as large as a horse.

42 1 9 0 2 R . R O S S

had again to trust to my own observation; in spite of all efforts no literatureon the subject could be obtained by me. It was also necessary to note and studythe ordinary parasites of these insects - of which I found a number during theensuing years. Indeed, at the commencement of the work I found one whichrequired careful working out. It was a pseudo-navicella occurring in the mal-pighian tubes of the brindled mosquitoes (Stegomyia). After a little study itwas ascertained that pseudo-navicellae have no connection with the parasitesof malaria, being the sporocysts of a species of gregarine. Next year Mansonpublished an account of these interesting organisms taken from my letters tohim26. I refer to them also in my publication at the end of the year 24.

The second method alluded to above was based on the following considera-tions. According to Manson’s more advanced hypothesis, the motile fila-ments, after living some days in the mosquito, would probably pass from itinto the water, on the surface of which we then supposed it usually died afterlaying its eggs. Such water then ought to be infective to human beings, eitherwhen ingested, or perhaps when inhaled as a vapour. It would be easy to testthis speculation by experiment. I caused a number of mosquitoes, both of thebrindled and grey varieties, to feed on a selected patient, and then kept themin large jars containing water at the bottom, until they died one by one. Thewater was then exposed to sunlight and otherwise allowed to remain in thecondition of marsh water. Different batches of fed mosquitoes were intro-duced into the jars from time to time so as to make sure that the water shouldindeed contain the parasites which by hypothesis should escape from the in-sects. In May 1895 I gave draughts of this water to three natives who volun-teered themselves for the experiment. All of them declared that they had notsuffered from fever for years.* Strangely enough one of the men developed amild but marked attack of fever in eleven days, the parasite being found in hisblood. I was naturally much pleased with the success of the experiment andbegan to hope that the mode of infection had been found; but the failure ofmany subsequent attempts of the same kind forced me later to reject any defi-nite conclusion on the point (section 11).**

11. Bangalore (1895-1897). Progress of work. Possessing abundance of material

* The experiment was justifiable owing to the slight degree of illness usually producedby malarial fever in natives when properly treated.** Owing to the interest of Surgeon Major Owen, the Maharajah of Patiala had at thistime offered the government of the Punjab to employ me at his own expense to study ma-laria in his dominions. The government of the Punjab, however, refused the offer.


together with plenty of leisure, I was now progressing excellently with myresearches (though without definite results) when I received my first interrup-tion. On the 9th September 1895, I was placed on special duty by the Govern-ment of India to combat a serious outbreak of cholera in the large town ofBangalore, and also to report on the general condition of sanitation there. Thisduty was of great interest and value to me because it afforded me an unrivalledopportunity for examining in the closest detail the general sanitation of atropical city - an experience which has stood me in good stead during lateryears. For four months, however, I was so busy with my new labours that Ihad little time for research. Bangalore I already knew well, having indeedmade some of my first studies of malaria there when staff surgeon of the townfrom 1890-1893. I now easily ascertained by the light of Laveran’s great dis-covery that the cases of fever which I had attributed to intestinal auto-intoxi-cation were nothing but examples of aestivo-autumnal infection among par-tially immunized natives. I found also that, as at Secunderabad, my brindledand grey mosquitoes abounded all over the place. I dissected a few mosquitoesas time allowed; and when my more arduous sanitary duties began to dim-inish in March 1896, I found that I could give an hour or two a day to thework. My results, however, remained constantly negative, in spite of theclosest scrutiny of many mosquitoes. At the same time I continued my at-tempts to produce infection by water.

In March 1896, Manson delivered the three Goulstonian Lectures at theRoyal College of Physicians in London, and again put the case of his hypoth-esis in an admirable manner, supporting his arguments largely upon my ob-servations of the previous year 2 6. He wrote to me frequently for fed mos-quitoes, which I sent to him whenever I could. He also urged me to keep onthe track of the flagellated spores; advised me to try infection experimentswith the insufflation of dried and powdered mosquitoes, and with the vapourof an "artificial marsh" in which fed mosquitoes had died. These devices didnot appear as promising to me as they evidently did to him. It was scarcelylikely that dead mosquitoes could do much in regard to the dissemination ofmalaria in nature, at least in the form of dust, owing principally to the factthat dead insects seldom escape the ants in the tropics. All dust, moreover, isgenerally subject to the intense heat of the sun which, except in the presence ofwater, must be very inimical to most unprotected organisms. The smallamount of time at my disposal was therefore devoted to the methods alreadyattempted.

Towards the middle of the year I had made nineteen experiments with a

44 1 9 0 2 R . R O S S

view to carrying infection by drinking water; and together with three morecases, I described these in a publication at the end of the year 30. Water, inwhich mosquitoes fed on cases of malaria had died, or which contained largenumbers of the pseudo-navicellae of the gregarines of mosquitoes, was givento various persons by the mouth. The majority of the attempts were entirelynegative: but nevertheless a slight but noticeable reaction did occur in threeof the whole number of twenty-two cases. This still remains a very curiouscircumstance; but the facts were published exactly as they were found, with-out the influence of the "personal equation". At the end of the paper I sum-marized my results and decided that the positive reactions, though interesting,were too few and too slight to warrant any definite conclusion.* I am nowinclined to think that they may have been due to the following circumstances.The persons on whom the experiments were made were generally low-casteindians who required a fee before drinking the water and also an assurancethat they would receive more if taken ill. Now it is well recognized that manynatives are constantly infected with malaria and get relapses on any extra-ordinary demand being made upon their systems, as by fatigue, chill, or dissi-pation. I have even heard it stated by medical men possessing large experienceof natives that they can often produce fever in themselves by exposure whenthey wish to do so. In this case at all events it was possible that some of thesubjects spent their preliminary fees in dissipation, thus producing the sup-posed reaction after the experiments.

These results not being as decisive as I had expected from the first experi-ment of the kind made in the previous year, I began to consider whether someother route of infection was not possible or probable; and it soon grew uponme that Mansons’s induction was exigent only as regards the entry of theparasites into mosquitoes, and that his secondary hypothesis regarding theirescape from the insects and their infection of man through drinking waterwas not so strong. I quickly thought of several other routes for infection -which will be examined presently; and first I considered it possible that theinsects, previously infected from diseased persons or possibly from other mos-quitoes, might then inoculate the parasites into healthy persons during punc-ture, or might deposit them on the skin during haustellation. It was easy to

*My actual words were, "While we cannot dream of stating definitely on the strengthof these experiments that there is something connected with the mosquito which is capa-ble of imparting fever, the three positive results are still curious and tend to be in favour ofthe truth of Manson’s theory." Yet one of my Italian critics has attempted to prove, byignoring this passage, that I pretended to have established infection by drinking water.


test this view immediately by experiment; and early in August I made a smallseries of observations which were published in the same paper30.

A number of mosquitoes all bred from larvae in captivity, and of all thekinds which I could collect (many specimens of brindled and grey mosqui-toes) were fed upon several patients with numerous parasites in their blood.One of these patients had all three kinds of parasites in him; and I speciallyemployed this case, as well as many varieties of mosquitoes, in order to in-crease the chances of one at least of the species of mosquitoes present beingappropriate for one at least of the species of parasites. After feeding, the insectswere kept alive for one or two days and were then applied in considerablenumbers on two occasions to Mr. Appia, Assistant Surgeon of the BowringCivil Hospital at Bangalore, who courageously volunteered for the experi-ment. Mr. Appia had suffered from malarial fever some years previously, butnot since then; so that if he should be attacked by fever shortly after the ex-periment, it would be strong evidence, if not proof, in favour of the inocula-tion theory. He remained, however, absolutely free from fever. He was thenbitten by five mosquitoes which had been partially fed immediately before on acase of crescents - on the supposition that the insects may carry the infectionmechanically, as the tsetse fly carries nagana; but the result was again negative.Lastly two other individuals were bitten by mosquitoes fed from three to fivedays previously; still without effect. I judged then, either that infection is notproduced in this way, or that the proper species of mosquitoes had not beenemployed, or that they had not been kept for the proper period after feeding;and I proposed to return to the subject again. It should be noted that theseexperiments of mine were made quite independently, and before I had heardof the theories of King and Bignami - as indeed was stated in another publica-tion of mine at the end the year32.

In July 1896 Bignami’s criticism of Manson’s hypothesis, referred to in sec-tion 6, appeared in Italy29. I heard nothing about it whatever, until I receivedManson’s letter of the 12th October, which was accompanied by a translationof the critique. Bignami’s paper was not a profound one, and consisted only ofa copious and dexterous rendering of ideas which were new only to those whohad not already fully considered the subject. His objection to Manson’s theorywas based principally on Grassi’s loose speculation that the motile filamentsare the result of the death of the parasites in vitro. As this was a vital point inthe chain of reasoning I now set to work to examine the subject experiment-ally, and was soon able to show that the escape of the filaments depends oncertain proper conditions, and not at all on the death of the parasites. Thus

46 1 9 0 2 R . R O S S

they escape more readily when the specific gravity of the blood is altered,either by the abstraction of water by partial evaporation or, as Marshall prov-ed, by the addition of a little water. On the other hand they do not escape atall, even when the parent cells perish, so long as the blood is kept scrupulouslyunchanged. In order to prove this, I drew the blood from the finger into asmall mass of Vaseline placed upon the skin, and then mounted the whole forthe microscope in such a manner as to prevent the blood coming even intomomentary contact with the air. The result was that not a single crescentemitted motile filaments or even underwent the preliminary change of spher-utilization, although it was evident they all died after a time.* This experimentcompletely disposed of the death-agony theory of the Italians. Previously tothis, however, Sacharoff had shown that contrary to Grassi’s statements, thefilaments do contain chromatin; but I could not procure a copy of his work32.I should add that after long observation of the filaments I could never bringmyself to believe that they are merely the result of the spasmodic movementsof dying protoplasm; and this tale was in fact never anything but a gratuitousassumption.

These researches were published later32,33, and were confirmed by Mansonand Rees in London37.

The conditions required by the crescents for emitting filaments were nowclearly seen to be those obtaining in the mosquito’s stomach, where the bloodis rapidly altered by abstraction of water; and I therefore continued my workwithout further reference to Bignami’s objection.

His view that infection may be caused by inoculation had already been con-sidered and experimented on by me, as just mentioned. But it should be under-stood that Bignami’s hypothesis (which was the same as that given long pre-viously and much more strongly by King) was very different from mine.King and Bignami thought that mosquitoes bring the poison from marshes toman; this speculation had not occurred to me until I read Bignami’s paper inOctober, and then it did not appeal to me at all, because it was self-evidentthat the connection between malaria and marshes could be sufficiently ex-plained by the fact that mosquitoes breed in stagnant water. My speculationwas that mosquitoes become infected from men (according to Manson’s in-

* If the preparation was opened and the blood momentarily exposed to the air withinsome hours after abstraction from the patient, the crescents could be seen at once to re-sume their functions. But if this experiment was delayed about 24 hours, the crescents nolonger reacted, and indeed showed clear evidence of death by their vacuolization andother structural changes.


duction) and possibly also from other mosquitoes, and then communicate theparasites to healthy persons - perhaps by inoculation. It will be seen whichview is right; but in consequence of my negative experiments, the inoculationtheory was not much favoured by me until I made my researches in the SigurGhat (section 12).

My duties at Bangalore continued for a year and a half At first placed uponspecial duty to report on the sanitation of the town (80,000 inhabitants), I wasafterwards appointed officiating Residency Surgeon there and was requiredto reorganize the whole of the sanitary arrangements, to create a health de-partment, to participate in a committee designated to reconstruct the munici-pal regulations, and to contend against several outbreaks of cholera. Conse-quently I did not possess as much time as at Secunderabad for my researcheson malaria, but nevertheless in addition to the experiments last referred to,I was able to dissect many hundreds of mosquitoes in pursuance of my princi-pal plan of campaign. Several agents were employed to collect the larvae of asmany kinds of mosquitoes as possible, especially from several spots whencemost of the cases of fever came; and these insects, belonging to many speciesof the brindled and grey groups of mosquitoes,* were all tested by directfeeding on cases of malaria, especially aestivo-autunmal. But though eachinsect was examined with the utmost care, almost every cell being scrupulous-ly searched for parasites, the results still remained entirely negative.

Towards the end of my stay in Bangalore, as failure followed failure, I wasnaturally forced to reconsider the whole basis of my work. But no; the mostcritical examination of Manson’s induction failed to exhibit any flaw in thefundamental reasoning. The gametocytes, and the process by which the mo-tile filaments escape from them after the blood is drawn from the patient,could only be meant for infection of the mosquito. There was no other ex-planation. Nature does not create these complex phenomena for nothing; andthe theory must be - was - sound. What then was the cause of my repeatedfailures? Was it possible that the kinds of mosquitoes which I had tested hith-erto - very many kinds - were all of the wrong species?

The reasons for and against this view were as follows. In all the districts andtowns of India in which I had served or stayed during fifteen years - Madras,Bangalore, Moulmein, the Andamans, Secunderabad, Upper Burma, Bom-bay, Poona, Calcutta, Karachi, Quetta, the Nilgherry Hills, malaria was un-doubtedly present, especially among the natives ; and in all of them without

* Not once as yet had I come across the dappled-winged mosquitoes ; though, be it noted,many of my larvae were collected from ditches and the edges of ponds.

48 1 9 0 2 R . R O S S

exception I remember to have noticed mosquitoes belonging to both the greyand the brindled classes. This naturally suggested a connection between thedisease and the insects; but, on the other hand, were not the later perhaps toocommon? So far as I could ascertain, the disease was generally limited to cer-tain spots and localities (by no means always near marshes); whereas the in-sects were everywhere, and were indeed often commonest at points were ma-laria was rare, as in the houses of Europeans. After all may not the true malaria-bearing variety or varieties have been overlooked by me? Possibly they werecomparatively rare species, or species occurring only at a certain season - ahypothesis favoured by the well-known fact of the seasonal variation of ma-laria. Now, as I was fully aware at the time, malarial fever is a relapsing diseasein which attacks continue to occur for years after infection; so that it does notfollow by any means that the infective variety of mosquito must always bepresent in a locality, even though numerous cases of malarial fever are present.And it was to be specially noted that most of the cases occurring in Bangalorewere probably only cases of relapse.

These arguments were not strong enough to be conclusive on either side ofthe question. I had done quite right in spending so much time over the greyand brindled mosquitoes; there was enough prima facie evidence against themto demand a full enquiry. But before spending more time over them it wasnow advisable to see whether further light could be obtained by epidemiolog-ical investigation. The towns in which I had worked hitherto could scarcelybe considered more than moderately malarious; I now proposed to visit anintensely malarious spot, at the height, too, of the malarious season in orderto ascertain what kind of mosquitoes prevailed there at the time; and reason-ably hoped that this kind would prove to be the guilty species.

Being a servant of Government I could not of course go where I pleasedwithout leave, and I therefore first attempted to interest Government in mywork. Owing to my representations, the United Planters’ Association ofSouthern India took up the matter; and the Honourable Mr. Bliss, Member ofCouncil of the Madras Government, and also Surgeon General Sibthorpe,head of the Madras Medical Service, were kind enough to give their warmassistance - for which I shall always be much indebted. The result was that theGovernment of Madras made a proposal to the Government of India that Ishould now be placed on special duty to investigate malaria. Most unfortu-nately, however, in addition to the plague, the Afridi war broke out just aboutthat time, and owing to the paucity of medical officers the Government ofIndia was obliged to reject the proposal - May 1896. But in the meantime I


had determined to begin the enquiry at once at my own expense during twomonths’ leave which was due to me; and accordingly, on the completion ofmy duty in Bangalore, I went to the Nilgherry Hills for the purpose of study-ing the point referred to in some of the intensely malarious plantations at thefoot of these mountains.

12. The Sigur Ghat (1897). I arrived at Ootacamund, the great hill station ofthe Nilgherry Hills, at the beginning of April, 1896. This station which isabout 8,000 feet above sea-level, is surrounded by numerous tea and coffeeplantations, scattered here and there in the rich valleys of the hills, and evenfor some distance out on the plains which encompass the hills like a sea. Afterenquiry it was determined to begin the investigation in the Sigur Ghat, a longnatural trench which cuts at one stroke from the Ootacamund plateau rightdown to the plain, and which had the worst reputation for malaria. A dâkbungalow (rest house) and a small plantation existed near the top of the trench,at a place called Kahutti about 5,500 feet above sea-level; and owing to thefact that a single night spent lower down the valley was thought enough toensure a bad and perhaps fatal attack, I determined to lodge here and visit thelower valley only during the day time. Nevertheless even at Kalhutti I foundalmost everyone suffering from fever - which was ascribed to miasmata float-ing up the ravine from the plains below; and I had been there only a few daysand had paid only one diurnal visit to the plain when I myself suffered a badattack of aestivo-autumnal infection, the diagnosis being confirmed by themicroscope.*

After two weeks’ energetic treatment with quinine I was well enough toresume operations; and this time went direct to the plantations at the foot ofthe Sigur Ghat. The owner of one of them, Mr. Kindersley, wise enough toreside in the hills during the intensely malarious season of the year, very kindlyplaced his house in the plantation at my disposal; so that I was able to make athorough survey of the locality. Both plantations are situated in the midst ofluxuriant forest and undergrowth close under the declivities of the mountains,* This case was remarkable for the brevity of its incubation period. I had never sufferedbefore from malaria, and was not likely to have acquired the infection either at Bangaloreor Ootacamund. I had arrived at Kalhutti at 6 pm on the 22nd April, and my attack com-menced at 10 p.m. on the 25th April. I ascribed it at the time to my visit to the plain madeon the 23rd April; but there is now little doubt that the infection was acquired at Kalhuttiitself, which was swarming with mosquitoes, and where the servant of the dâk bungalowand all his family were ill. At the same time I do not remember to have been bitten bymosquitoes, and said so in my published account.

50 1 9 0 2 R . R O S S

and are copiously watered by irrigation channels. Almost all the native em-ployees, as well as some families of aborigines, were suffering from severemalaria - anaemia, emaciation, and enlarged spleen; and the parasites wereeasily found in the blood of some of them. But I was not a little astonishedwhen I discovered that mosquitoes appeared to be almost absent in all thehouses. In spite of considerable rewards which were offered for their capture,and in spite of the efforts of my trained servants and myself, scarcely any weresecured. I was informed indeed by some of the employees that they were oftenbitten at night by insects which escaped in the morning; but these nocturnalvisitors were not procurable *. Later however, we were told of some insectswhich haunted the jungle and bit in the daytime under the trees. I found theseto be a small kind of brindled mosquito, and strongly suspected that theymight be the culpable species; and accordingly examined them closely andcalled them Culex silvestris.

A part of my mission here was to enquire whether the mosquitoes in thishighly malarious spot did not contain parasites which were not contained inthe mosquitoes of the less malarious Bangalore. If they did so these parasitesmight reasonably be suspected of being the mosquito stage of the malariaparasite; and the question could subsequently be tested by experiment. Thesemosquitoes were at once found to contain two new kinds of parasites, namelycrowds of active swarm-spores in the intestine, and, secondly, clusters ofspores (each cluster containing eight bright oval spores) in the ventral nervoussystem. A close study was made of these organisms; but they did not appearin some of the jungle mosquitoes which had been fed on patients. Strangelyenough, however, a person who volunteered to swallow a number of theswarm-spores in water was attacked subsequently with fever, the malariaparasites, however, not being found in his blood; but I heard afterwards that,contrary to his statements, he had had fever just previously.

It will be remembered that Manson’s secondary hypothesis suggested thatthe motile filaments, after living for some time in the mosquito, pass from itinto the water, and thence by ingestion or inhalation into man. My experi-ence, however, tended to convince me that if such infection of water takesplace at all it must be very limited - in other words, that after their escapefrom the dead mosquito, the organisms can neither travel far in the water norlive long there. For if they could do this, almost all water in India would beinfected, and the disease would be universal, instead of being confined, as it is,to certain spots. For the same reason the miasmatic theory never appealed* Judging by our present knowledge, these must have been the offenders.


strongly to me. I thought it most likely that men became infected from smallstores of drinking water such as wells, cisterns, and even pots and ewers, intowhich infected mosquitoes often fall and die while laying their eggs - a theorywhich would easily account for the isolation of the malady, because, as I hadobserved over and over again, mosquitoes seldom wander far from theirhaunts. As, according to hypothesis, the organism escapes from the gnat intothe water in which she lays her eggs, it followed that water which containedmost larvae should contain most malaria parasites, and, conversely, that drink-ing water free from larvae would probably be free from parasites. Now inattempting to apply these considerations to the case of the Sigur plantations,I found them at once opposed by many facts. Not only were there few adultmosquitoes there, but the larvae could be found only in a few stagnant puddlesin the depth of the jungle, while the drinking water was obtained from rapidstreams just issued from pure mountain springs, in which larvae neither existednor were likely to exist.

These facts again forced me to reconsider the whole of Manson’s secondaryhypotheses, and to search for more plausible theories. Three such theories oc-curred to me. I had long observed that while they are sucking blood, gnatsdeposit minute drops of excretae on the skin every ten seconds or so; and Ihad actually shown that these drops may contain the pseudo-navicellae of gre-garines. It was therefore possible that they might contain the spores of theparasites of malaria, which might then be able to work their way through theskin and into the blood of the victim. Another hypothesis of mine was thatthe malarial spores might be voided by the insects, not upon the skin, but uponrotting vegetation or damp earth (e.g. the floor of the houses and huts of na-tives), and might there possibly develop into some extracorporeal form cap-able of infecting man by air-borne spores.* The third theory was that infectedmosquitoes could in some mysterious manner introduce the parasites directlyinto the blood during the acts of puncture and haustellation. This view was

* This was by no means an idle conjecture, and was indeed strictly based upon the anal-ogy of Cunningham’s life history of the Amoeba coli, which that observer stated was void-ed from the intestines of cattle and afterwards formed pseudo-plasmodia in the exposeddung-men and cattle being infected by the air-borne spores of these pseudo-plasmodia.He thought that the organisms were related to the Mycetozoa and called them Protomyxo-myces coprinarius. His important statements have been ignored but not disproved by sub-sequent writers. Similarly I thought that the parasites of malaria might possibly be ex-tracted from the circulation by mosquitoes, be deposited by them upon the damp floorsof dwelling houses and there develop in a like manner. This hypothesis was at that time ascogent as any other.

52 1 9 0 2 R . R O S S

similar to that of King and Bignami, with this difference that while these ob-servers thought that the mosquitoes derived the parasites from marshes, I held,in consequence of Manson’s induction, that they derived them from patients.In the account of my work in the Sigur Ghat which was published a fewmonths later40 it was stated that this was the hypothesis which I now held tobe the probable one.*

It was during these researches that I first noticed the "dappled-winged mos-quitoes". While looking for mosquitoes in a vacant rest house at the foot ofthe ghat I captured an insect resting in a peculiar attitude with the body-axis atan angle to the wall (as I noticed at the moment). On examination, its wingswere found to have a series of black marks along the anterior nervure; but asI saw no more individuals of the species, I did not think the observation to beof sufficient importance to be included in my paper. Yet, had I only known itat the time, this was the very species I was in search of!

Indeed the whole of this investigation afforded a clear example of the well-known ambiguity of epidemiological work. Of the kind of insect which wasreally causing the disease at the time, I saw but a single individual! The reasonis now quite apparent. Unlike the grey and brindled mosquitoes which rest inthe dark comers of dwellings by day in large numbers, many species of dap-pled-winged mosquitoes fly out at daybreak. It is true that other species ofthis genus have more domestic habits and can therefore be more easily found;and if fortune had been my friend in those days she would have brought meto a place where these species abound - such as places afterwards visited by mein Assam and the Darjeeling Terai. Nor does it follow in any case that thepredominant species of mosquito in a locality must be the malaria-bearingspecies there; there is no reason why the innocent species should not out-number the dangerous species even in the most malarious spots: while lastly,it is now known that the dangerous species may abound where there is no

* I said, "On the whole from a consideration of the epidemiological facts I should be in-clined to favour the idea of contact being the mode of infection; and may add that one ofmy servants who was employed in catching the adult silvestris by allowing them to settleon his legs and arms was attacked five days afterwards by the quartan parasite". By con-tact I meant contact of the mosquito with the skin as explained further on by the followingwords : "Since the presence of a human being in the jungle at once causes a number of sil-vestris mosquitoes to attack him on all sides, it is very clear that he may readily be infectedby their agency, either by injection of the parasite through the puncture, or by its deposi-tion on the skin in the shape of spores contained in the insect’s faeces, which, observationshows, are always discharged in quantity during the act of haustellation". My theories re-garding infection are also referred to in my previous paper30.


malaria at all. Hence, though I did not know it at the time, it is impossible toindicate, much less to certify, the malaria-bearing species by its numerical rela-tions with other species in malarious localities.

One of the principal results of my work in the Sigur Ghat was that it led meto doubt the probability of infection by drinking water. I should have likedto remain there much longer; but on the expiry of my leave was forced toreturn to my regiment at Secunderabad, five hundred miles away, and wasnever able to visit the place again.*

13. Secunderabad (1897). The fundamental discovery. On my return to Secunde-rabad (July 1897), the first thing I noticed was that the malaria had continuedunabated during almost two years since I had left; if anything it was worse,and many recruits who had recently joined the regiment had been attacked -as they averred, for the first time. This clearly showed that these cases were notmerely relapses, and that some cause of infection was actually at work amongthe troops. It was for me to discover the cause; and I determined to return tomy old method, and to test experimentally all the kinds of mosquitoes preva-lent anywhere near the barracks. I had now been studying the subject almostconstantly for over two years, and had become so very familiar with the mi-croscopical appearance of the various structures of the mosquito** that I feltthe mosquito stage of the parasite could no longer escape me if it existed at all.Numerous "cases of crescents" suitable for the experiments were in my hos-pital, and it was obvious from the number of fresh cases occurring that theproper kind of mosquito must be somewhere about. If I failed it could onlybe because there was some flaw in Manson’s induction.

At the same time a possible fallacy was detected in the logic of that part ofthe theory which suggested that the motile filaments after their escape fromthe parent cells in the mosquito’s stomach must take up their abode in the tissuesof the insect. The vital and inevitable part of the induction consisted only ofthe reasoning which inferred that the stomach of the mosquito is the naturallocus for the escape of the motile filaments. It was only conjecture to say thatthey must enter the tissues; because for all we knew it was possible that theymight remain in the intestine for some time and then be voided, probably insome altered form, either upon the ground or upon the human skin (see my

* I had been offered an appointment in Berar, but had declined it in order to carry onthese researches in the Sigur Ghat. I suffered severely for this later on.** This does not mean that I was equally familiar with the macroscopical anatomy of themosquito - a subject which has only recently been dealt with fully.

54 1 9 0 2 R . R O S S

hypotheses in the previous section). It was therefore now necessary to examinethe evacuations as well as the tissues of my subjects.

I commenced work by making a careful survey of the various kinds of mos-quitoes which were to be found in the officers’ quarters, in the regimental hos-pital, and in the numerous little houses of the native soldiers, which consti-tuted the barracks or "lines", as they were called. I found first, the insects withwhich I was familiar during my previous studies here in 1895, namely (a)several species of brindled mosquitoes, and (b) two species of grey mosqui-toes. But at the same time I was astonished at observing that the whole placewas overrun by swarms of (c) a small and delicate variety of mosquitoes,which were at once observed to rest with the body-axis at an angle to thewall, and which had spotted wings. In fact they were evidently of the samegenus (though not of the same species) as the mosquito which had been previ-ously found in the Sigur Ghat - a genus, or perhaps family, quite distinct fromthose of the grey and brindled mosquitoes with which I had hitherto beenworking.

It is now time to speak more particularly of all these mosquitoes. I had writ-ten repeatedly to Manson, to various booksellers in England, and to severalpersons in India who I thought might help me, for some literature on the sub-ject; but could obtain nothing except a few notes by popular authors, such asThomas, who wrote on piscatorial subjects in India. I could not even obtainany adequate works on the anatomy of insects in general. Of Ficalbi’s workon European gnats - which would have helped me immensely - I was igno-rant, and received no copy. Manson had found the name of one species ofmosquito which I sent to him; but this did not help me, for what I requiredwas a scientific work on the structure and classification of the mosquitoes asa group. I was therefore obliged, as mentioned in section 10, to trust to myown rough methods of classification; and these were based, not on the criteriaof entomologists, such as the structures of the mouth parts or the nervures ofthe wings, but on the general appearance and markings, the eggs, the habits,etc., of the insects. It was only the working classification of an amateur with-out literature to guide him, and made for his own convenience; but, as eventshave proved it was roughly correct. Up to July 1897 I recognized the twofollowing groups :

(a) Brindled mosquitoes ( now recognized as belonging to the genus Stegomyia,Theobald). Body and legs boldly marked black and white, or brown andwhite. Wings plain. Biting voraciously, mostly in the day-time. Resting withabdomen hanging towards the surface of attachment, and the last pair of


legs tilted on the back. Breeding mostly in pots of water. Larvae floating headdownwards and possessing short stumpy breathing tubes. Eggs black, oval,and laid separately.

(b) Grey mosquitoes (now recognized as belonging to the genus Culex, Linn.as defined by Theobald). Back barred with transverse brown and white stri-pes. Legs and wings plain. Biting somewhat timidly, mostly at night. Restingwith abdomen hanging towards surface of attachment. Breeding mostly inwooden tubs, ditches, garden cisterns, and drains. Larvae floating head down-wards and possessing long breathing tubes. Eggs elongated and somewhatlanceolate and laid simultaneously in "rafts".

I had found mosquitoes of the same genera, though possibly of differentspecies, at Bangalore and at several spots in the Nilgherry Hills; and also atBombay, Poona, and Madras during short visits made to these cities in con-nection with my sanitary duties at Bangalore. I remembered also to have seensimilar insects in Burma and the Andamans; so that it was reasonable to sup-pose that they constituted the common or ordinary kinds of mosquitoes inIndia. The new mosquitoes which I now and subsequently met with, andnamed dappled-winged mosquitoes, were evidently of quite another genus tothe foregoing, and were distinguished by me by the following characteristics:

(c) Dappled-winged or spotted-winged mosquitoes (now recognized as belong-ing to the genus Anopheles, Meig.). Body, legs, and proboscis marked brownand white, or dark and light brown. Wings with several dark blotches on ornear the anterior nervure. Resting with abdomen pointed outward from thesurface of attachment. Body more elegant, and shaped like that of a humming-bird moth. Breeding mostly in natural pools of water on the ground. Larvaefloating flat on the surface of the water like sticks, and possessing no breathingtube at all. Eggs laid singly; cohering in triangular patterns, and shaped like anancient boat with raised prow and stem, and surrounded with a membranewhich - when the egg is seen in profile - gives the appearance of a bank ofoars to the boat.

In the spotted-winged mosquitoes which I now found at Secunderabad Inoticed at once the general difference of shape, the peculiar attitude of the in-sects when at rest, the marks on the wings, and the appearance of the eggs (asseen within the body of the female when dissected); but the larvae could notbe studied until later.* The adults were very delicate, pale-brown creatures,which by common consent seemed scarcely to bite man, though they were

* It was principally my assistant, Mahomed Bux, who ascertained, as a general rule, theattitude of the larvae.

56 1 9 0 2 R . R O S S

numerous enough to have caused much irritation had they done so. Theyswarmed in my own quarters, but seldom bit me. They abounded also in thehouses of the other officers of the regiment, who, with their families had re-mained quite free from malarial fever. Consequently I was not disposed tothink that they had anything to do with the disease. On the other hand thegrey mosquitoes swarmed in the barracks, but were much less numerous inthe officer’s quarters (situated some hundreds of yards to leeward of the bar-racks). Suspicion therefore first attached to the latter variety.

I determined, however, not to be swayed by such considerations, but tomake a most complete and exhaustive test of all the varieties which I couldprocure - even at the cost of repeating much of my old negative work, duringwhich, laborious as it was, I may have overlooked the object I was in search of.A number of natives were employed to collect larvae from far and wide roundthe barracks. These larvae were kept in separate bottles, and when the adultinsects appeared they were released within mosquito nets in which the patientswere placed. The insects were applied sometimes during the day in a darkenedroom; and were sometimes fed all night. After feeding, the gorged insectswere collected in small bottles containing a little water and were kept forseveral days before being dissected. The procedure was therefore the same asbefore; but now, in order to ensure at least definite negative results, redoubledcare was taken; almost every cell was examined; even the integument and legswere not neglected; the evacuations of the insects found in the bottles, and thecontents of the intestine were scrupulously searched; at the end of the firstexamination staining reagents were often run through the preparation, and itwas searched again with care. The work, which was continued from 8 a.m.to 3 or 4 p.m. with a short interval for breakfast, was most exhausting, and soblinding that I could scarcely see afterwards; and the difficulty was increasedby the fact that my microscope was almost worn out, the screws being rustedwith sweat from my hands and forehead, and my only remaining eye-piecebeing cracked, while swarms of flies persecuted me at their pleasure as I satwith both hands engaged at the instrument. As the year had almost been rain-less (it was the first year of plague and famine) the heat was almost intolerable,and a punkah could not be used for fear of injuring the delicate dissections.Fortunately my invaluable oil-immersion object-glass remained good.

Towards the middle of August I had exhaustively searched numerous greymosquitoes and a few brindled mosquitoes. The results were absolutely nega-tive; the insects contained nothing whatever. Then, I think for the first time,I began to feel that the long quest had been in vain and that a flaw existed some-


where in the induction. The disease was there, the mosquitoes were there -how was it that I found nothing? I may perhaps be pardoned for dwelling onmy personal feelings during that time, and the astonishing time which fol-lowed. Science too has its drama; and the actor on that real scene cannot helpbeing moved when he remembers it - although it may appear trivial enoughto others.

I had remembered the small dappled-winged mosquitoes, but as I couldnot succeed either in finding their larvae or in inducing the adult insects tobite patients, I could make no experiments with them. On the 15th August,however, one of my assistants brought me a bottle of larvae, many of whichhatched out next day. Among them I found several dappled-winged mos-quitoes, evidently of the same genus as those found about the barracks, butmuch larger and stronger. Delighted with this capture I fed them (and theyproved to be very voracious) on a case with crescents in the blood. Expectingto find more in the breeding bottle and wishing to watch the escape of themotile filaments in this new variety, I dissected four of them for this purposeimmediately after feeding. This proved to be most unfortunate, as there wereno more of these insects in the bottle, and the results as regards the motilefilaments were negative. I had, however, four of the gorged dappled-wingedmosquitoes left; but by bad luck two of the dissections were very imperfectand I found nothing. On the 20th August I had two remaining insects bothliving. Both had been fed on the 16th instant. I had much work to do withother mosquitoes, and was not able to attend to these until late in the afternoonwhen my sight had become very fatigued. The seventh dappled-winged mos-quito was then successfully dissected. Every cell was searched, and to my in-tense disappointment nothing whatever was found, until I came to the insect’sstomach. Here, however, just as I was about to abandon the examination, Isaw a very delicate circular cell apparently lying amongst the ordinary cells ofthe organ, and scarcely distinguishable from them. Almost instinctively I feltthat here was something new. On looking further, another and anothersimilar object presented itself. I now focussed the lens carefully on one of these,and found that it contained a few minute granules of some black substanceexactly like the pigment of the parasite of malaria. I counted altogether twelveof these cells in the insect, but was so tired with work and had been so oftendisappointed before that I did not at the moment recognize the value of theobservation. After mounting the preparation I went home and slept for nearlyan hour. On waking, my first thought was that the problem was solved; andso it was.

58 1 9 0 2 R . R O S S

Next morning I returned to the hospital with much apprehension lest theeighth and last dappled-winged mosquito should have died and become de-composed during the night. It was alive; and was killed and dissected withmuch anxiety. Similar bodies were present in it, only they were distinctly larger.The seventh mosquito had been dissected four days after finding; the eighthfive days after feeding; the parasites in the latter had lived a day longer thanthose in the former and were consequently larger. Both insects had been bredfrom larvae in captivity; both had been fed for the first time on the sameperson - a case of malaria; no such objects as these pigmented cells - as I thencalled them - had ever before been seen in the hundreds of mosquitoes exam-ined by me; the objects lay, not in the stomach cavity of the insects, but in thethickness of the stomach wall; all contained a number of black granules pre-cisely similar in appearance to those contained by the parasites of malaria, andquite unlike anything which I had ever seen in any mosquito previously.Lastly, these two mosquitoes were the first of the kind which I had ever tested.*

The mind long engaged with a single problem often acquires a kind ofprophetic insight, apparently stronger than reason, which tells the truth,though the actual arguments may look feeble enough when put upon paper.Such an insight is mainly based, I suppose, on a concentration of small proba-bilities each of which may have little weight of itself; but in this case at allevents the insight was there and spoke the truth.

These two observations solved the malaria problem. They did not completethe story, certainly; but they furnished the clue. At a stroke they gave both ofthe two unknown quantities - the kind of mosquito implicated and the posi-tion and appearance of the parasites within it. The great difficulty was reallyovercome; and all the multitude of important results which have since beenobtained were obtained solely by the easy task of following this clue - a workfor children. We may rest assured that if these observations had not been madewe should still have remained ignorant of the mode in which this importantdisease, with its annual death roll of millions, is propagated - aye, and wouldhave remained ignorant of it until some one else had taken up the same in-vestigation by the same method.

And no other method would have solved the problem. It was necessary to

* On the assumption that these cells had developed from the motile filaments it was dif-ficult at the moment to explain the pigment within them - as the motile filaments have nopigment. I thought it possible, however, that after fixing themselves in the stomach wallthey might be able to derive haemoglobin from the contents of the organ, and afterwardsconvert this into the pigment.


find not one but two unknown quantities, and neither could be found by it-self. There are no phenomena which would serve to indicate the kind of mos-quito. In nearly all malarious places there are many kinds of mosquitoes, and,as in the Sigur Ghat and other places, the malaria-bearing species are in noway predominant among them either in numbers or in any other way. Indeedthe malaria-bearing species occur in places where malaria has not been knownin the memory of man, as around Liverpool. By what process of reasoningthen could we isolate the species? It might possibly have been practicable todetect it by a very long series of experiments aimed at infecting men by thebites of successive species of mosquitoes; but no one would have undertakensuch a work without the guide of a very strong theory in favour of inoculationby the bite; and the theory of King and Bignami to this effect was little morethan a conjecture. It was not likely that the first species tried would have givensuccessful results, as my own experiments of 1896 showed. Even if, after amultitude of costly and dangerous experiments, a positive result had been at-tained by this method, it would always be open to doubt (seeing that theexperiments would have to be done in a malarious country) whether the casewas not merely one of relapse; and another long series of experiments wouldbe required to eliminate this doubt. And then, even when the proper speciesof mosquito was detected, there would still be no guide to the form and posi-tion of the parasites within it, or even to the way in which they enter the insect(Bignami thought that they enter the larvae from marsh water). No, the thingwas not practical. Bignami himself abandoned his experiments on his owntheory after the first failure29 and did not resume them until after my workhad clearly indicated both the kind o mosquito implicated and the route offinfection. The only practicable method was to attempt to find both unknownquantities simultaneously by the "trial and failure system" - such as I adopted.*

The discovery of the pigmented cells, therefore, ended for me at least theold research, the period of doubt, the groping in the dark. The secret springhad been touched, the door flew open, the path led onward full in the light,and it was obvious that science and humanity had found a new dominion.But it was necessary to follow the clue forthwith; to watch the developmentof the pigmented cells in mosquito after mosquito; to ascertain what becameof them; to fathom the mystery of the route of infection; and then to savehuman life in the gross, perhaps to open continents to civilization.

* I mention these facts because many writers on the subject seem to think that the originaldiscovery was made merely by catching the first mosquito and finding the pigmentedcells within it.

60 1 9 0 2 R . R O S S

The first thing was to obtain more - hundreds - of these large dappled-winged mosquitoes. Alas, the man who had found them had, contrary to myorders, put the larvae from many sources in the same bottle! All the larvaefrom all these sources were collected - but no more dappled-winged mos-quitoes! I turned then to the small but similar variety which swarmed aboutthe barracks. Being evidently of the same genus, they too would probablyharbour the parasites; but though my men and myself searched high and lowfor their larvae, we could not find them. I could scarcely even persuade theadults to lay their eggs in captivity.

Thinking that in spite of all my care I may have overlooked the pigmentedcells in the grey and brindled mosquitoes, I now searched for them in thestomachs of a number of these, but without result. A number of the smalldappled-winged mosquitoes caught about the hospital were also examinedfor them in vain. These observations served however for a "control" on thetwo positive cases.

Owing to the great heat at Secunderabad I had been obliged to leave myfamily at Ootacamund, and was now compelled to go to Bangalore for a fewdays in order to settle them there for the remainder of the summer. This gaveme leisure for writing a report to the government of India on the discovery ofthe pigmented cells, and also a short paper on the same subject for publication.The latter was of course intended only as a preliminary to a detailed reportwhich I hoped to be able to publish in a few months and which I thought

Fig.2. Pigmented cells (zygotes) of aestivo-autumnal parasite in dappled-winged mos-quitoes (Anopheles). From Ross’s paper, British Medical Journal, 18th Dec. 1897, p. 1787.


would contain the full explication of the whole problem. I described mymethod in a few opening lines, being careful to note that the mosquitoes usedby me had been "bred in bottles from the larva". The mosquitoes were thendescribed as well as possible - the spots on the wings and the peculiar shape ofthe eggs being noted, but reference to the peculiar attitude being inadvertentlyomitted. Next I gave in detail the circumstances under which the pigmentedcells were found, together with a description of them; and finally discussed,very guardedly, their probable relation to the parasite of malaria. I hadbrought the original preparations with me, and now showed them to myfriend Surgeon Major John Smyth, who at my request kindly added a note tomy paper, corroborating my description. They were then despatched by postto Manson. My paper, however, did not appear until December38; but whenit did so it was accompanied by an excellent drawing of the pigmented cellsfurnished at the instance of Manson, and also by remarks of Manson, BlandSutton, and Thin, who discussed the new objects - the last holding that thecells were ordinary cells of the stomach wall into which malarial pigment hadentered in some manner from the stomach cavity. This preliminary articlewas published by me for the express purpose of guiding the researches ofothers; and in fact anyone who had read my description of the pigmented cellsand of the dappled-winged mosquitoes would now have had little difficultyin repeating my work.*

On my return to Secunderabad I was much disappointed to find that thelarvae of neither the large nor the small species of dappled-winged mosquitohad yet been collected. Consequently in the intervals of searching for them,I spent my time in examining the stomachs of all the mosquitoes I could catchfor the pigmented cells. I hoped especially to find them in the small dappled-winged insects caught about the hospital, where there were several cases ofmalaria, but was disappointed. On the 18th September, however, a large greymosquito was observed feeding on a patient suffering from the benign tertianparasites and was promptly secured. The stomach was full of black blood, sothat it must have fed previously (freshly imbibed blood showing red in theinsects) as well as on this occasion. It was kept until the 21st and was thendissected. To my delight the pigmented cells were again found, in consider-able numbers; but they were larger even than those of the mosquito of the21st August. As this particular insect had not been bred from the larva in cap-tivity I could not say for certain where it had become infected, but I thought* This is exactly what was done by the Italian observers fifteen months later (see sec-

tion 23).

62 1 9 0 2 R . R O S S

it likely that it had been feeding on the case of tertian all the time (that is, fromabout a week before it was killed) as the patient was in a bed by himself in acorner of a large nearly empty ward. Hence I naturally inferred as a probabil-ity that the pigmented cells in this insect were derived from that case; and Ithought that their large size suggested that they must have been so derivedabout a week before the insect was killed. But of course I could not speakwith absolute assurance on these points.*

Meanwhile swarms of small grey larvae had been found in an isolated poolof rain-water, which I had overlooked because it was on the top of a hillockwhere pools were not likely to exist. On hatching out, these were found to bethe long-sought larvae of the small dappled-winged mosquitoes. I observedat once that they had no breathing tubes and that their attitude was peculiar ascompared with the larvae of other mosquitoes; and noticed also that the poolin which they were found seemed too shallow and evanescent for the latter -facts shown by me and my colleagues in 1899 to be of the greatest importancein connection with the prevention of malaria. Directly enough of the adultsappeared from the larvae in the breeding-bottle, they were released in largenumbers within the mosquito-net of a patient with crescents in his blood.Next morning only two of them were found to have fed themselves. Onewas killed next day, but nothing was found in it. The second was killed theday after, and was found to contain a large number of very small pigmentedcells! This really almost clinched the matter; for three out of four dappled-winged mosquitoes bred from the larvae in captivity and fed on cases of cres-cents had been found to contain pigmented cells; while these cells could notbe seen in insects of the same kind which had not been so fed. Just at this timeI wrote to Manson, in a state of unbounded delight, that he might expect toknow the full life-history of the parasites of malaria in the mosquito within afew weeks.

Next day however, I received telegraphic instruction from Governmentordering me to proceed forthwith to Kherwara in Rajputana - a place a thou-sand miles distant !

14. Interruption (September 1897-February 1898). It would be difficult for othersto understand the effect of this cruel blow. Here in Secunderabad I had numer-ous cases of malaria in my own hospital, and, moreover, the men had beentrained to submit to mosquito bites - a matter often of some difficulty with* This mosquito also contained a number of the swarm-spores which I had observed inthe Sigur Ghat.


the superstitious natives of India. I had also experienced assistants hired bymyself for the work; and, above all, the proper kind of mosquitoes, includingtheir larvae, just found in abundance. There is no doubt whatever that, had Ibeen left at Secunderabad, I could easily have traced the whole life-history ofthe human parasites in dappled-winged mosquitoes within a few weeks. Butat Kherwara I did not know what would happen. It was in the north; winterwas approaching; and I knew that mosquitoes would refuse to bite in the cold.I failed even to guess the reason for this sudden transfer. The astonishing dis-covery of the pigmented cells had been officially and fully reported to theGovernment through the chiefs of my own department; malaria is the mostimportant disease of India; and I thought that my superiors were taking thegreatest possible interest in researches which touched so vital a subject - Ithought that they would make every effort to leave me undisturbed, if not togive me active help.

But the orders were peremptory and not to be discussed. Within two days(26th September) I was on the week’s journey to Kherwara. I saw only onegleam of comfort. It was impossible that my chiefs, medical men, would con-sent to interrupt my work at such a moment. There must undoubtedly be abad outbreak of malarial fever at Kherwara which would throw great lighton my subject.

When I arrived at the place however - a petty station with three or fourEuropeans (whom I shall always remember for their kindness), and part of anative regiment of Bhils, isolated in the midst of miles of wild country farremoved from civilization - I was told that there was no malaria there; therehad not been a case for months !

This then was my Elba - almost my île du Diable; and I saw no prospect ofescaping from it for a year at least. After excusing myself from accepting theappointment in Berar, I had indeed later asked to be remembered for a per-manent appointment to which I thought my long service (more than sixteenyears) and my work at Bangalore had at least given me some claim. But thiswas only a temporary and insignificant one, generally held by juniors; and Ido not know why the transfer was made, unless possibly (though not certain-ly) for reasons connected with the Afridi war. At all events it was made with-out reference to my researches. I wrote officially to my superiors, begging tobe allowed to return to Secunderabad to continue my work; but receivedonly a reprimand in consequence. There was no escape; but my pension wasdue to me the following April, and I made up my mind to apply for it as soonas the war was over, and to continue my researches as a private person.

64 1 9 0 2 R . R O S S

The cold weather came on apace, and at first it appeared to be utterly im-possible to work. There were no cases of malaria and scarcely any mosquitoes.Much to my pleasure, however, I found a few dappled-winged gnats, andobserved again that their larvae lived in water on the ground - namely in a pitand an old well - apparently almost as dormant as the adults were. I kept asingle one alive in a bottle for two months without its developing.

Shortly after arrival at Kherwara I wrote down a brief account of the find-ing of the pigmented cells in the third and fourth mosquitoes. At the end ofJanuary the British Medical J ournal containing my previous paper on thecells38, together with remarks by Manson, Bland Sutton, and Thin, reachedme. I therefore rewrote the beginning of my second paper; and added a refer-ence to some work which I had been able to do with pigeons, and also a longdiscussion of Thin’s remarks, in which I showed that his position with regardto the pigmented cells was untenable. The paper was published in February.I did not explicitly say that the third dappled-winged mosquito had been bredfrom the larva in captivity, because it was evident that this fact would be in-ferred from the opening of the first paper of which the second was obviouslya continuation. But I said that the grey mosquito in which pigmented cellshad been found was "observed feeding on a patient", and that "I judged formany reasons that it had been feeding occasionally on the same man for severaldays" showing clearly enough that this insect had not been bred from thelarva in captivity. The facts might have been put more explicitly at the time;but they are apparent enough to any candid reader.* In the paper the order ofthe third and fourth mosquitoes is changed for purposes of description - thecase of the grey mosquito being put last because it was doubtful.

The work with pigeons just referred to was as follows. Being unable to ob-tain cases of human malaria I turned to the malaria of birds which had longbeen known to harbour parasites closely similar in appearance and life-historyto the malaria parasites of man. Both Manson and I had long recognized thetechnical advantages of working with these organisms. I immediately foundthe parasites of Labbé’s genus Halteridium in the pigeons of Kherwara; butcould not induce mosquitoes to bite the birds. Observing, however, that theywere infested by a species of blood-sucking fly, I examined thirty of these, and

* When I wrote these papers I did not suspect that every line of mine, even in some ofmy private letters, would be subjected to a minute and unscrupulous analysis in the hopeof finding discrepancies which would serve to discredit my observations. Every possibleartifice has been used for this purpose by the very men who learnt all they knew fromthese very publications.


some lice, fed on infected pigeons. No pigmented cells were, however, foundin them.

At last when the weather became warmer in February several cases of quar-tan fever occurred among the troops, probably relapses. The dappled-wingedmosquitoes still refused to bite; but I succeeded in feeding a number of brin-dled mosquitoes of a peculiar brown species on the cases. The results were againnegative in thirty-four of these insects.

I was just about to apply for my pension when welcome news arrived. I hadof course given full details of my sudden transfer to Manson; and he had ex-erted himself to influence the government of India and the Director Generalof the Indian Medical Service (then Surgeon General Cleghorn) to put me onspecial duty to continue my researches. I had urged the same thing upon theDirector General; but, unfortunately as it happened, suggested that one goodplace for the work would be Assam, where an epidemic of kala-azar - a diseasewhich Rogers had recently reported to be malaria - had long been raging.However, I now received a telegram stating that I had been placed on specialduty to investigate malaria and kala-azar in Calcutta and Assam for sixmonths.* My five months’ imprisonment was at an end. I arrived in Calcuttaon the 17th February 1898; and was joined there by my family, with all mybooks and notes which had been with them at Bangalore all this time.

15. Calcutta (February-April, 1898). The theory proved. Now in recompensefor the tribulations of Kherwara, opened a glorious time, during which theamazing story of malaria was unrolled little by little. The great induction hadgiven the clue; now, following the clue step by step, we were to be led intoregions where Nature revealed herself wonderful beyond the imagination ofany of us. In the background was something greater still - the possibility ofsaving human life on the large scale.

I am happy to be able to begin this part of the narrative with a brief accountof the brilliant and important discovery of MacCallum. It will be rememberedthat Manson had thought the motile filaments to be flagellated spores; that Ihad studied them much without being able to learn anything new about themexcept that they are certainly living organisms; and that when I finally foundthe pigmented cells I thought that these were derived from the motile fila-ments, and had absorbed their melanin from the haemoglobin in the stomachcavity of the insects. In his letter of the 11th August however, Manson sentme a paper by Simond, suggesting that the similar motile filaments of certain* Afterwards extended to one year.

66 1 9 0 2 R . R O S S

Coccidia are not of the nature of flagellated spores at all, but of the nature ofsperms35. How were these facts to be reconciled?

In a letter dated the 17th November 1897 Manson informed me that a dis-covery had been made by W. G. MacCallum in America regarding the motilefilaments, showing independently that they are of the nature suggested bySimond’s work. He did not send me the literature; and as his letter reachedme at Kherwara I could not then obtain it. Shortly after my arrival at Calcuttahowever, I procured a copy of the Lancet36 which gave an abstract of Mac-Callum’s work. The discovery was as follows.

In 1897 MacCallum undertook a study of the motile filaments. Workingwith the Halteridium of birds he noticed first that the gametocytes seemed tobe of two kinds, namely one kind which produced the motile filaments, andanother kind which did not do so. On watching two of these cells, one of eachkind in the same field of the microscope, he observed (July 1897) that the fila-ments escaped from one as usual; that it moved about actively for a time; andthen approaching the other gametocyte actually entered it. Other observa-tions of MacCallum and Opie, made both on Halteridium and on the cres-centic gametocytes of the aestivo-autumnal parasite of man, confirmed thisbeautiful discovery. The fact, as previously shown by Sacharoff, that the fila-ments contain chromatin was now explained; and also the facts that theyescape and move about in the blood. They are, indeed, sperms which are emit-ted from the one kind of gametocytes, the males, and which fertilize the otherkind, the females. Thus these minute parasites, among the lowest of creatures,have their sexes, and a form of sexual reproduction precisely like that of thehighest animals.

More than this, MacCallum observed in the case of Halteriditim of the crowthat the female cell, motionless before fertilization, afterwards becomes elon-gated and vigorous, and moves across the field in vitro. This motile form hadapparently long been seen by Danilewski and had been called by him a vermi-cule.*

So much for the motile filaments, but now what were the pigmented cells?Everyone seems to have thought that as soon as the flagellate spores disappear-ed, so did Manson’s theory. But it was not so. The induction remained asstrong as before; the locus of the phenomenon was still in all probability the

* I should certainly have observed these facts when I was making a special study of themotile filaments in 1895 and 1896. I repeatedly saw them apparently attacking leuco-cytes42. The reason why I found that only a percentage of crescents emit the filaments inthe mosquito’s stomach is now explained the remainder were females (section 11).


stomach-cavity of the mosquito. MacCallum’s work seems to have reachedManson shortly after my discovery of the pigmented cells came to him. Heconnected the two groups of facts in a moment. My pigmented cells were thevermicules, or fertilized female cells, which had burrowed into the insect’s tissues for thepurpose of undergoing further development there. This, and not my hypothesismade before MacCallum’s paper was known to me, explained the presence ofpigment in the cells. He communicated his views to me in his letter of the 7thFebruary, and published them later41.

Meanwhile, after another struggle, I was again in sight of the pigmentedcells. On my arrival at Calcutta I found myself installed in the convenient littlelaboratory which had been formerly used by Professor D. D. Cunningham.There was a native assistant there; but I hired at my own expense several oth-ers, especially a most intelligent Mahommedan named Mahommed Bux, whoafter he had been trained showed great enthusiasm and gave me much assist-ance. To my delight I at once noted several varieties of dappled-winged mos-quitoes, besides many kinds of grey and brindled mosquitoes, actually withinthe laboratory, and found the breeding-places of the latter just outside. Thoseof the dappled-winged mosquitoes were detected a little later; and were againseen to be pools of water on the ground. The next thing was to obtain cases ofmalaria; but here I was met by an unexpected and most unforeseen misfor-tune. The plague had been raging all this time in India; and on the Govern-ment’s trying to introduce Haffkine’s prophylactic inoculation in Calcuttajust before my arrival, serious riots, during which many of the Europeans hadfelt themselves obliged to go about armed with revolvers, had occurred. Theignorant populace, thinking that the British were trying to inoculate themwith and not against plague, flew into paroxysms of terror at the very sight ofa European hakim (physician), while anything remotely resembling inocula-tion made them frantic. The physicians of the Calcutta hospitals were evident-ly very unwilling that I should use their cases for my experiments under thesecircumstances; and, as I had no hospital of my own as in Secunderabad andBangalore, I was forced to send my assistants into the bazaar (native parts ofthe city) in order to try to induce patients to come to me on payment. Calcuttais not very malarious, especially at that time of the year, and it was only onlarge payment that several beggars with fever were induced to come to me;but when I proposed to prick their fingers in order to examine their bloodthey generally left their money, took up their crutches, and fled without aword! This placed me in complete perplexity as to what to do, until I remem-bered the malaria of birds. A number of crows, pigeons, weaver-birds, spar-

68 1 9 0 2 R . R O S S

rows, and larks were then immediately procured, and experiments com-menced on them without delay.

The malarious parasites of birds are exceedingly closely related to those ofmen, and together with these and the malaria parasites of bats and monkeysform a group which is quite distinct from the intracorpuscular protozoa ofsome mammalia, such as the Pyrosoma bigeminum of cattle, and of reptiles, suchas Drepanidium. The true malaria parasites (namely the intracorpuscular proto-zoa of man, birds, bats, and monkeys) are distinguished by their generallyamoeboid character, by their possession of the characteristic black or brownpigment (melanin), and by an identical life-history as regards the productionand appearance of the spores within the corpuscles, and of the motile filamentsshortly after the blood containing them is drawn from the host. The parasitesof birds differ from those of man only in some very small morphological de-tails; and are so similar that in the earliest sub-classification of the group byGrassi, one of the parasites of birds commonly called Proteoroma is placed withtwo of the human species, the quartan and tertian, in one genus; while theother parasite of birds, commonly called Halteridium, is placed in anothergenus together with the remaining parasite of man, that of the pernicious,remittent, or aestivo-autumnal fevers. The latter part of Grassi’s classificationwas wrong; and we now recognize that both the parasites of birds must beplaced in one group with the quartan and tertian parasites of man; while thethird human species must be placed in a group by itself, owing to the distinctshape of its gametocytes (crescents). Thus zoologically, the avian species areactually more nearly related to two of the human species than these are to thethird human species. Anyone who had actually studied all these parasites,moreover, would have little doubt that they would be found to possess prac-tically identical life-histories outside the vertebrate hosts, or at least life-histo-ries which, if not identical, would be closely similar. It did not of course followwith certainty that the carrying agents of the avian parasites would be thesame as those of the human species; but we could safely assume that they wouldbe some kind of blood-sucking arthropod. At all events it was certain that thediscovery of the life-history of the avian parasites would immediately open upthat of the human organisms; while the practical difficulties of working withbirds and infecting them would be less than with men. In fact I should havebeen wise to have begun my researches with birds in 1895. I therefore deter-mined to employ birds at once pending the subsidence of the plague-scare,when I purposed of course to return to the human parasites; and there is nodoubt that this was the right course.


It was first advisable to see whether mosquitoes would not carry one or bothof the avian parasites. A number of crows and pigeons had been found to con-tain Halteridirium; but without waiting to examine the other birds, I placed onecrow, two pigeons, four larks and six sparrows in several cages all within thesame mosquito netting, and then in the evening released within the net a num-ber of grey and brindled mosquitoes bred from the larva in captivity. Nextmorning many of the grey mosquitoes were found gorged and were collectedand kept for several days according to my rules. On the 13th and 14th MarchI dissected them one by one. When thirteen had been examined with negativeresults I began to fear that I had committed myself to another tedious searchfor the proper kind of host of the avian parasites. But fortune was kinder onthis occasion; the fourteenth mosquito had pigmented cells precisely similarto those which I had found in the dappled-winged mosquitoes fed on patientswith crescents.

Next I examined the larks and sparrows used in this experiment togetherwith the crows and pigeons, and found that they contained not Halteridiumbut Proteosoma; so that it was doubtful from which kind of parasite the pig-mented cell had been developed. Consequently I now put the birds with Halteri-dium in one net and those with Proteosoma in another, and released within bothnets numbers of grey mosquitoes bred in the same bottle. Of thirty-four ofthese fed on the birds with Halteridium all were negative; but out of nine fedon the birds with Proteosoma, no less than five contained pigmented cells.

This result was obtained on the 20th March and practically proved the mos-quito theory of malaria. Out of hundreds of grey mosquitoes previously ex-amined none had contained pigmented cells except one which had beencaught feeding on a case of tertian (section 13), and one which may have bit-ten one of the birds with Proteosoma in the experiment of the 14th March.Now, however, no less than five out of nine fed on birds with Proteosomacontained them. Mathematically therefore the probabilities were enormous(amounting almost to certainty) in favour of the view that the pigmentedcells in this experiment had been derived from the Proteosoma.

The cells were in the tissues of the insect; the parasite must therefore beable to make its way into and live in mosquitoes; precisely similar cells hadbeen found in mosquitoes fed on men with malaria - and the chain of proofwas complete.

But the fact that the pigmented cells in the mosquitoes are indeed derivedfrom the parasites in the birds was of such fundamental importance that it re-quired the most formal and rigid proof - especially as no life-history of a pro-

70 1 9 0 2 R . R O S S

tozoal organism able to transfer itself from one host to another was thenknown to science.*

I therefore now commenced a long series of differential experiments inorder to establish the fact thoroughly. Grey mosquitoes bred from the larva incaptivity were fed (a) on birds with Proteosoma and (b) on birds without Pro-teosoma, and the results compared. The details will be found in my Report-Q.Out of 245 grey mosquitoes fed on birds with Proteosoma, 178, or 72 per cent,contained pigmented cells, while out of 249 of them fed on blood containingother parasites or no parasites, not a single one contained them.

Another experiment was the following. Three sparrows were selected, onewith no parasites, one with a few Proteosoma, and one with many Proteosoma.They were placed in separate nets, and numbers of grey mosquitoes from thesame breeding bottle were fed simultaneously but separately on them. Tenmosquitoes fed on each bird were then examined, and the total number ofpigmented cells in all of them were counted. The results from a hasty enumer-ation made by myself were as follows. No pigmented cells were found in theten mosquitoes fed on the sparrow without parasites; 292 in the ten mosqui-toes fed on the sparrow with a few Proteosoma; and 1009 in the ten fed on theone with many Proteosoma 42. The preparations were sent to Manson, whomade a more careful enumeration and found 0, 571, and 1084, pigmented cellsin the three sets of mosquitoes separately41.

The fact then was proved, and the theory that the parasites of malaria de-velop in mosquitoes was practically established. Meanwhile I had been pro-ceeding in the fascinating task of watching the progress of that development.A number of grey mosquitoes would be fed on an infected bird and would bedissected two, three, four days, and so on, afterward. It was thus found that thepigmented cells grew rapidly in size until about the eighth day, when they be-came so large as to be almost visible to the naked eye. At this point they seemedto become mature; and it could be seen that many of them burst within theinsect; because mosquitoes which had been infected more than eight or ninedays before dissection were found to contain not the mature pigmented cells,but only their empty capsules. For the moment I could not ascertain whatbecame of their contents.

This part of the work led to an interesting observation which influenced allsubsequent researches on mosquito-borne disease. It will be remembered thatManson had always thought that a few days after her meal of blood the female* The life-history of Pyrosoma in ticks is not even yet known; and the transference of try-panosomes by flies appears to be merely mechanical.


mosquito laid her eggs and died; at this moment he considered both filariaeand malaria parasites escape into the water from the insect26. I had acceptedthis view, but had frequently observed that the insects do not die immediatelyafter laying their eggs; and now, as I watched the pigmented cells growinglarger and larger without apparently ripening, even five days after the insectwas fed, it occurred to me that we had been allowing our mosquitoes to die soearly owing to a very simple reason - we had omitted to feed them again! Itherefore fed my infected mosquitoes a second and a third time, and more;and found that I could easily keep them alive for a month.* This enabled me towork out the development of the malaria parasites completely; and also help-ed others subsequently to find a further stage in the development of filariae,and to ascertain the mode of infection in yellow fever.

I did not succeed, and, indeed, scarcely attempted to find the host of Halteri-dium. Nor was there time to work out the formation and behaviour of the"vermicules" in the stomach cavity of the mosquito - although this could havebeen done very easily; but on one occasion I saw the motile vermicule ofcrow’s Halteridium in a brindled mosquito.

Of course all this time anxious efforts had been made to obtain cases of hu-man malaria for experiment. Early in March I succeeded after much difficultyin finding an old beggar with a few crescents willing to submit to the dreadedoperations; and I examined 41 grey mosquitoes and 15 dark greenish dappled-winged mosquitoes which had been fed on him. The first kind were triedmerely as controls, and were of course negative; but, much to my surprise anddisappointment, so were the latter. I attributed the failure to the facts that thecrescents were very scarce in the patient, that the mosquitoes fed very sparing-ly, and that there was a spell of very cold weather (for Calcutta) at the time.A few unsatisfactory experiments with grey mosquitoes fed on a child withmild tertian parasites also failed. In spite of all efforts no other cases could beprocured.

A full list of all these experiments, beginning with my earliest work in 1895,will be found in my Report written a few weeks later42.

Recognizing, of course, the inadequacy of my nomenclature for mosqui-toes and the urgent necessity for employing the correct entomological namesfor the various species used by me, and having failed to obtain any literatureon the subject, I now applied for assistance at the Indian Museum in Calcutta ;but I received a brief reply to the effect that the savants there could give me no

* I refed them on healthy birds ; but Bancroft subsequently found that they could be keptalive for some time on bananas.

72 1 9 0 2 R . R O S S

information on the subject. Once more I had to depend on myself; and I there-fore took special note of the dappled-winged mosquitoes found near my la-boratory. No less than four species were detected - a large brown species, alarge greenish one (with which the experiments just described were made), asmall black one, and a small brown one. The first was named later by Gilesfrom specimens brought to England by me, and was called by him Anophelesrossi; and from the studies of Stephens and Christophers made in Calcuttasome years subsequently it is almost certain that the second species was A. fu-liginosus.

Numerous specimens of Proteosoma in grey mosquitoes were sent to Man-son on the 30th March.

By the middle of April I had overworked myself, and was obliged to ask forten days’ leave to the Himalayan hill-station Darjeeling, where I hoped fortime to write my report in a cool climate. I had heard also of several intenselymalarious spots at the foot of the Darjeeling mountains, and hoped to be ableto carry on there the studies on human malaria which were debarred in Cal-cutta and at the same time to continue my work on avain malaria. I thereforeleft Calcutta on the 17th April.

16. The Darjeeling Terai (April-June, 1898). Efforts to obtain assistance. The re-sults with Proteosoma were obviously so important that it was necessary to givethem to the world at once, in the hope that many observers would now beeasily able to follow the work, and also that I might obtain assistance in con-sequence of my success. Consequently I devoted my time at Darjeeling towriting a report to my chief, the Director General of the Indian Medical Ser-vice, on my latest work. The report begins with a brief statement of my firstdiscovery of the pigmented cells,* followed by a list of the experiments, bothpositive and negative, which I had made with a view to infecting mosquitoeswith human malaria. Then comes a detailed account of experiments and posi-tive results with Proteosoma, followed by a minute description of the neces-sary technique, and of the appearance, position, and development of the pig-mented cells. Next I discuss several points, including the bearing of MacCal-lum’s work on mine. As I had brought my microscope and some of my speci-mens with me, I was able to add to the report large plates giving drawings ofthe pigmented cells up to the stage to which they had as yet been traced.** Thework was, however, hurriedly executed, as I had only a few days in which to* In the twelfth line the word "ordinary" is a slip of the pen for "other".** These plates are reproduced at the end of this publication.


write it. The pigmented cells are called in it "proteosoma-coccidia", a termwhich has been criticized. I thought at that time that the parasites of malariareally belong to the Coccidiidae, the early stages of their life being passed inman and birds, and the later stages (to which the name Coccidia might moreappropriately be attached) in the mosquito; just as the early and later stages ofthe sexual forms of C. oviforme occur respectively in the bile ducts and the in-testine of the rabbit. At the end of the report a description of the grey andbrindled mosquitoes with drawings is furnished by Mr. G. C. Dudgeon, agentleman who was acquainted with entomology; and the report concludes

Fig. 3. From paper by Manson, British Medical Journal, 18th June, 1898, p. 1577. (After Ross’sdrawings.)

74 1 9 0 2 R . R O S S

with the words, "These observations prove the mosquito theory of malaria asexpounded by Dr. Patrick Manson..."

The report after some delay, was dated 21st May, and was despatched atonce, with an urgent request that it might be published as soon as possible. Tomy surprise I was informed that publication was not allowed without the per-mission of the Secretary of State for India. This meant writing to England andseveral months delay; but the report was printed very soon and numerouscopies were sent at the end of June to Manson for private circulation amongpersons interested in malaria. In the meantime my success had been describedin detail both to Laveran and Manson in letters dated 22nd April - the lettersbeing accompanied by a series of seventeen more preparations; and, as myresults could not be published by myself, I now asked Manson to publish themfor me.

On the 18th June Manson published an able paper on the subject. The articlecommences with a resumé of my orginal discovery of pigmented cells in dap-pled-winged mosquitoes fed on a human patient with malaria, and gives thereferences to my papers describing the observation41. It goes on to describe thenew results with Proteosoma; giving drawings of the pigmented cells up to thesixth day of development, and a diagram showing the connection betweenMacCallum’s observation and my own; and it concludes with letters fromNuttall and Laveran accepting my results. Laveran said, "It appears to me tobe undoubted that the elements discovered by Dr. R. Ross in the stomach ofmosquitoes fed on the blood of birds, the subjects of haemosporidiosis, arereally parasites, and that these parasites represent one of the phases of the evolu-tion of the haematozoa... I have shown the preparations to M. Metchnikoff,who shares my opinion".*

This paper drew general attention to my work, to which previously littlecredence had been attached; and, as many of my preparations had been sent toEngland and France, not only were those competent to form an opinion en-abled to judge of the truth of my statements, but those who wished to followmy steps were now easily able to do so. In fact a most amusing comedy nowcommenced, in which we witnessed the hasty efforts of those who had beensceptics, not only to follow my steps but to persuade the world that their la-bours were original. During several years since that date every observation ofmine has been independently discovered by various writers.

Recognizing the vast significance of these preliminary results with Proteo-

* Owing to a misapprehension, this paper erroneously states that Halteridium also hadbeen cultivated.


soma, and also feeling that it was quite beyond the power of one man to com-plete as quickly as the interests of humanity demanded the work which re-mained to be done, I now made strong efforts to obtain assistance. The help ofa single medical man to collect mosquitoes and cases of malaria for me wouldcertainly have enabled me to reach the last proofs in a month or two; and be itremembered, the mortality from fever in India alone is said to amount tosomething like ten thousand persons every day. When, however, I asked theDirector General for the services of one or more junior medical officers, I wastold that none could be spared at the time. As a matter of fact there are alwaysmany medical officers in military employment in India, who can be spared ifthey are urgently called for; and the truth is that the necessary trouble was nottaken. I then wrote to Manson begging him by all means in his power to ob-tain assistance for me from England; and thought that the Royal Society,which is subsided to a small amount by Government, might afford to give it.The matter was considered; and it was finally agreed to appoint, with the helpof the Colonial Office, a commission of three gentlemen to investigate mala-ria. Two of these were sent in the autumn to study the subject - in Italy; and,after much difficulty, the third was allowed to come to me. He arrived atChristmas with orders to stay for two months - not to help me but to verifymy statements!

That was all the help I received. The excuse is that my work had not beenconfirmed. But it had been accepted by Laveran, Manson, Metchnikoff, andNuttall, who at least knew the subject. Was not this enough to justify the ex-penditure of a few hundred pounds in so great a cause? I mention these factsbecause it was largely this failure to obtain assistance which drove me fromIndia some months later; which delayed the completion of my work for morethan a year, and which postponed the adoption of an energetic prophylaxis inIndia until the present. Not mine the fault: the truth is that for some inexpli-cable reason men will never recognize the transcendent importance of investi-gation into the causes of those great diseases which destroy them.

The rest of my time in this district was spent in making attempts to find asuitable place in the intensely malarious areas at the foot of the mountains forresearches on human malaria. This alone was a matter of no little difficulty, asthe locality was new to me and I could obtain no accurate information regard-ing the disease. I worked especially at a place called Punkabari, situated a fewhundred feet above the plain. A hospital and plantation existed here, and therewas a large village some miles away on the plain. But the results were not grati-fying; few dappled-winged mosquitoes could be found, as the rainy season

76 1 9 0 2 R . R O S S

had not yet commenced; while to my grief I discovered that the plague-scarewas, if anything, stronger here than in Calcutta. So terrified were the natives,that on one occasion, when one of my men shot a sparrow for me in the vil-lage, all the coolies in the neighbourhood ran away for miles into the jungles,costing the planters much money and trouble before they could be induced toreturn. In fact I was given to understand that scientific investigations were notrequired there at the moment! Indeed it soon became apparent that I was onlywasting much valuable time; and I consequently determined to complete myresearches on Proteosoma at Calcutta without further delay.

17. Calcutta (June-August, 1898). The route of infection. On my return to Cal-cutta (4th June) I found it still quite impossible to obtain cases of human mala-ria for my work, and therefore proceeded at once with the life-history of Pro-teosoma. The most wonderful of all the phases of this history was now to berevealed. I had traced the development of the pigmented cells up to their ma-turity and subsequent rupture and discharge of their contents into the body-cavity of the grey mosquitoes. I could not see at the moment what happenedto these contents; yet upon this point depended the vastly important ques-tion of the route of infection in malaria. But, when I had broken off my worka few weeks previously, the contents had appeared to consist of little more thana pure fluid.

Hitherto my mosquitoes had been dissected in water or a weak solution ofsalt, and I had had no time for methodical staining. A strong salt solution wasnow used and the secret was revealed. The contents of the mature pigmentedcells did not consist of clear fluid, but of a multitude of delicate thread-likebodies, which, on the rupture of the parent cell, were poured into the body-cavity of the insect, and which were evidently spores.

Fig. 4. Sketch of thread-like bodies (sporozoids or blasts) escaping from mature rup-tured pigmented cell (zygote). From letter of Ross to Laveran, dated 18th July, 1898.


What happened now to these spores in view of the theories mentioned insection 12? Did they escape into the water according to Manson’s ideas; orwere they voided by the intestine according to mine; or did they in somemysterious manner work their way into healthy persons during puncture,according to the theories of King and Bignami and later of myself? But thestaff of theory was no longer necessary; plain research would suffice.

Here there was another sharp but short struggle. I saw that the thread-likebodies, although apparently without motion themselves, were soon scatteredby the insect’s circulation all through its body; but beyond this I could notfollow them for some time, in spite of the most assiduous endeavours. Theyseemed to have been created without object.

On the 2nd July however, I found in the thorax of a mosquito a large cellwhich, surprising to state, contained within it several of the thread-like bodies.They were able then to work their way into cells; but what was the cell? Onthe 4th July, while working upon another mosquito, I found that the thread-like bodies seemed to become more and more numerous towards a point inthe thorax - as if they were converging toward some destination. At that pointthere were numerous cells such as I had seen on the 2nd July. They were at-tached to a duct and were all contained within the same capsule - they con-stituted in fact some kind of gland. In all these cells there were hundreds of thethread-like bodies, floating loosely at all angles to each other like fish in globesof glass. Close by was another lobe of the gland similarly full of the spores.I was at the summit but not on it. I did not know what the gland was. I knewthe appearance of the cells it is true, but in spite of my thousand and more dis-sections I had by no means acquired a full knowledge of the macroscopicalanatomy. I found it by no means easy to meet with the gland again. On the8th July the mystery was solved. The gland lay in the neck and upper thorax-

Fig. 5. Thread-like bodies (sporozoids) in cells of salivary gland of mosquito. From letterof Ross to Laveran, dated 18th July, 1898.

78 1 9 0 2 R . R O S S

Fig. 6. Salivary gland of mosquito. From letter of Ross to Manson, dated 6th July, 1898.

the throat of the mosquito. It consisted of three lobes on each side. The ductsof each lobe unite together like the midrifs of a trefoil. The duct so formedruns forward and meets the similar duct of the other side under the chin - so tospeak - of the mosquito. The common duct advances still further and entersthrough the round base of the central stylet or stabbing weapon of the mosqui-to’s proboscis. It was easy now to recognize the nature of the gland; it was thesalivary gland, which secretes the irritating fluid which the mosquito injects inthe wound made by her in the skin, perhaps to dilate the vessels, perhaps toprevent speedy coagulation of the blood.*

The exact route of infection of this great disease, which annually slays itsmillions of human beings and keeps whole continents in darkness, was reveal-ed. These minute spores enter the salivary gland of the mosquito and pass withits poisonous saliva directly into the blood of men. Never in our dreams hadwe imagined so wonderful a tale as this.

But still all this was inference only; the last proof was demanded. If the in-fection can be given in this way, give it. I had long possessed in the laboratoryfive old birds - four sparrows and one weaver-bird - which had been keptthere for my "control" experiments, because they had never been found tocontain Proteosoma, even after several examinations. On the 25th June, as soonas I began to suspect the destination of the thread-like bodies, these birds wereall examined again, and were found to be still quite healthy. On that and thefollowing nights, a large number of grey mosquitoes which had been longpreviously fed upon infected birds and many of which had been found to con-* This gland had been discovered in 1888 by Macloskie5, but I did not know it at the timeand still had received no literature on the subject.


tain the thread-like bodies in their salivary glands, were released within a mos-quito-net in which the five healthy birds were placed. On the followingmornings I satisfied myself that the infected mosquitoes had gorged them-selves freely on the birds; and then, fascinated by the study of the parasites inthe salivary glands of mosquitoes, I forgot all about even this important ex-periment.

Now only a small percentage of birds in Calcutta are infected with Proteo-soma. Out of 111 wild sparrows examined by me I found the parasites only in15, or 13.5 per cent. Moreover, even in infected birds, the parasites were scarce,seldom more than one being found in each field of the microscope. On the9th July I suddenly remembered my experiment and examined the previouslyhealthy birds. All of them without exception were now found swarming withProteosoma, as many as twenty or even more being found in each field.

But not content even with this I repeated the experiment over and overagain; and within the next few weeks I succeeded in infecting 22 out of 28healthy sparrows (79 per cent), and also a crow and four weaver-birds, and,moreover, gave a more copious infection to four sparrows which previouslycontained only a few parasites. At the same time I kept as controls a numberof healthy birds in mosquito-nets, safe from the bites of mosquitoes, and foundthat none of them became infected (with one exception probably due to anerror).

Manson, to whom I had sent full details, told me that he would expound all

Fig. 7. Thread-like bodies (rods, sporozoids) in salivatory glands of mosquito. Publishedfrom Ross’s drawing by Manson, British Medical Journal, 24th September, 1898, p. 852.

80 1 9 0 2 R . R O S S

my results, with demonstrations of my specimens, at the meeting of the Brit-ish Medical Association to be held at Edinburgh at the end of July. I now an-nounced the successful infection of birds to him by a telegram, which reachedhim just as he was setting out (though ill at the time) for the meeting; and hewas therefore able to communicate the complete life-history of the parasitesin his address.

His exposition as Dr. Charles said, "created quite a furore", and was quicklymade known everywhere. His paper was published on the 24th September43

and gave a full account of the subject up to the infection of healthy birds, to-gether with several drawings of the thread-like bodies, both free and in thesalivary glands, taken from my letters.

It was interesting during these researches to watch the gradual invasion ofthe birds by the parasites. From five to eight days after they were bitten by in-fected mosquitoes no parasites could be found in their blood; then a few ap-peared; then many; and at the last large numbers. The first five birds all died,and so did some of the others; and their liver was found to be full of the char-acteristic pigment of malaria. But many recovered, the parasites graduallydecreasing in number.

At the same time I was temporally not a little delayed by finding inside themature pigmented cells certain large brown or black bodies which I provi-sionally thought might be connected with their life-history. As proved by theresearches just described, malaria could be carried by mosquitoes from thesick to the healthy, but as we know malaria clings intensely to location. Ittherefore seemed not at all unlikely that these black bodies, occurring as theydid actually within the pigmented cells, might be of the nature of sporocystsmeant in some way to infect other mosquitoes - so that the infection mightnot only be carried from man to man by the mosquito, but from mosquito tomosquito; or they might be meant to infect man, as Manson had thought,through the water. It was of course necessary, for sound science, to examinethese bodies; and I therefore tried to infect both birds and the larvae of mos-quitoes by feeding them on insects containing these black spores; but the re-sults were negative. Subsequently I saw reason to doubt whether the blackspores really had any connection with the parasites (section 20).

But there was little time for such researches, necessary as they seemed at themoment. Although there could be no doubt that the human parasites have thesame history as Proteosoma, still it was a necessary formality to complete thepartial demonstration of this fact which had been already attained, if only topersuade Government to take active measures against the disease; and I was at


last free to undertake the work. But now precisely occurred my last and mostannoying interruption.

Before coming to this, however, let us consider the results which had al-ready been attained and which have been the basis of nearly all that has beensubsequently done.

(1) The general life-history of Proteosoma in the grey mosquito and themode of infection being now ascertained, we could foretell to a practical cer-tainty that the life-history and mode of infection of all the other parasites ofthe same group, including the human ones, would be closely similar in alltheir stages; that is, that if they differed at all, they would differ only in smalldetails. The result of this was that if anyone wished to trace the life-history ofany of these organisms in a second host he would now find the task an ex-tremely easy one, because (a) he would know exactly the appearance of theparasite he was in search of, and (b) he would know exactly in what part ofthe anatomy of the second host to look for it. And if he wished to ascertainwhether a given animal was or was not the second host of the parasite, he couldeasily make sure of the fact by ascertaining whether or not it harboured thedescribed parasites, after feeding and dissection by the methods laid down byme.

It is in fact solely by this means that we have been able to demonstrate theproper hosts of the human parasites in many parts of the world.

(2) More than this, the pigmented cells of the aestivo-autumnal parasite ofman had been demonstrated to be exactly similar to those of Proteosoma on thesecond, fourth, and fifth days after infection of the mosquito; and the hosts ofthis important organism were shown to be at least two species of a specialgenus which could be recognized by its possessing spotted wings and boat-shaped eggs (section 23); and were clearly shown not to be my grey andbrindled mosquitoes, the former of which had been described sufficiently forrecognition39,42 .

(3) The important law that not all species of mosquitoes can harbour agiven parasite of this group had been established, both with regard to theaestivo-autumnal parasite and Proteosoma and Halteridium; and several im-portant facts regarding mosquitoes had slowly become evident to me - butwere not published until later.

(4) Lastly full directions of technique had been given in my report42. Theseconsisted of numerous essential details, acquired during several years’ expe-rience, regarding dissection and feeding, etc. - without a knowledge of whichthe observer would be very likely to go wrong (as for instance by attempting

82 1 9 0 2 R . R O S S

to section his mosquitoes for searching for the parasites, and omitting to feedthem regularly and change their soiled habitations for clean ones).

On the other hand my researches had given little or no information aboutthe quartan and tertian parasites - except of course the all important analogywith Proteosoma. The observation of the grey mosquito caught feeding on thecase of tertian was doubtful (section 14). Moreover they had not directly andabsolutely demonstrated the final stages even of the aestivo-autumnal para-sites in the dappled-winged mosquitoes, nor the mode of infection. But never-theless they had reduced the demonstrations still required to an easy formalitywhich was within the capacity of any tyro with sufficient material and a mi-croscope.

I am sorry to have to write such a summary of my work as this one; but itis rendered necessary by those who, during the long interruption of my la-bours which now followed, were able to work out some details of the subjectbefore me, and who have wished to conceal the assured fact that their effortswere simply a repetition and imitation of mine. It should be pointed out that,by a generally recognized zoological rule, the discovery of the life-history ofProteosoma in mosquitoes covers that of other members of the same group oforganisms, which have precisely the same development. By that rule, the rightof priority in discovery belongs to him who first works out the life-history ofone species of a group of animals; not to those who merely perform the easytask of extending the known facts to other species. Discovery is discovery; thedetermination of parallel facts, the filling in of details, the publication of prettyillustrations, and the furnishing of formal proofs of matters which are alreadycertain, are useful - but do not constitute discovery.

My infection experiments on birds were completed early in August, and, aswill be related presently, I was now no longer able to defer my work on kala-azar. Consequently I was obliged to leave Calcutta on the 13th August for mynew duties - much exhausted by work and heat in the plains. Before doing so,however, I released my host of little feathered prisoners, which had unwil-lingly been of such assistance in the investigation.

It should be mentioned that from the first discovery of the thread-like bod-ies I had wondered whether they have any other destination besides the sali-vary gland. The eggs were especially suspected, but the results of investigationwere negative. I therefore now concluded that malaria is communicated onlyby the bites of insects.

RESEARCHES ON MALARIA 83

18. Darjeeling district (August—September, 1898). Kala-dukh. It was mentioned at the end of section 14 that I myself had proposed to Government that kala- azar should be included in the programme of my year's special duty; because I then hoped that this disease might shed light upon the mosquito theory; but now when the theory was established and it was necessary to press on with the study of the human malaria, I wished to escape this additional duty, as I dread- ed lest it should involve me in much pathological work which would interfere with the principal line of research. I hinted as much to the Director General, but was told that he expected me to adhere to the programme. The disease was exciting much comment because it was new and was taking some thousand lives annually in Assam; but it was forgotten that malaria, though it is not new, takes some millions of lives annually in India alone!

Harold Brown had recently studied a disease which existed at the foot of the Darjeeling mountains, and which was called kala-dukh (black sickness) and was evidently closely allied to kala-azar (black fever). Consequently I obtained permission to investigate this disorder first, partly because an opportunity might be afforded me of making further studies at the same time on malaria in my old haunts at Punkabari. Fixing my head quarters at Kurseong in the hills on the road to Darjeeling, I made numerous visits to this locality, but was dogged by ill-luck. The plague-scare, though waning, was still present; and difficulties of transport impeded the work. On the 25th August I arrived at Naxalbari, an intensely malarious plantation and village on the plain beyond the foot of the hills, and found swarms of small and large dappled-winged mosquitoes (probably Anopheles listoni and A. rossi). There was no time to make formal experiments, and the people would not have allowed them; but I examined some dozens of these mosquitoes caught in the houses of infected persons, both for the pigmented cells and the thread-like bodies; but without success.* Nearly all my time was however taken up in pathological enquiries on kala-dukh - as I feared would be the case. But now it was no longer possible to postpone the evil hour without dereliction of duty, and I was obliged to set out on the long journey to Assam.

19. Assam (September—November, 1898). Kala-azar. I arrived at Nowgong, the centre of the epidemic of kala-azar, on the 13th September. It was at once obvious that my worst fears were well-founded, and that I would be plunged

* How unfortunate I was in this respect may be gathered from the papers of Stephens and Christophers71 who later found many of these mosquitoes infected in this very district.

84 1 9 0 2 R . R O S S

for months into a difficult pathological problem and a long pathological re-port. But the work was not without interest, and I may be pardoned for touch-ing upon it briefly. The disease had been first noticed by McNaught in 1882.A few years later Government sent Giles to investigate it; and Giles, whoprobably did not come much in contact with the real disease, seemed to havebeen considerably misled, and in a report (which was nevertheless a very ableone) pronounced the malady to be ankylostomiasis77. Many of the practi-tioners in the locality were not satisfied, however, and in 1896 Governmentsent Rogers to make a further report. Rogers certainly saw the real disease andconcluded that it was a virulent form of malaria78. As it was evidently com-municable, this implied that he held malarial fever to be communicable - athing which no one would believe at that time; but he maintained his opinionswith great courage and success. I was now sent in order, if possible, to decidethe question; and as my researches had shown that contrary to accepted viewsmalaria must be communicable from the sick to the healthy, Rogers’ positionwas justified. But the exact nature of kala-azar still required definition; and, asI was called upon to judge between opposite opinions, I was forced into atedious enquiry - though it was my immediate personal impression that thedisease is malaria.

Mixed with the cases of kala-azar there were numerous cases of ordinarymalaria; and I found that the local practitioners could not distinguish whichwas which until the cases became exceedingly severe, when they were declaredto be kala-azar. This generally happened only in the later stages of the cases - sothat in fact kala-azar seemed to be simply another name for a very severe andfrequently fatal form of malarial cachexia. As, moreover, many of the pa-tients had ankylostomes, those who are familiar with the subject will under-stand that my task was indeed a complex one. The plague-scare not havingpenetrated here, I attacked the problem by examining the blood of all thecases, both of malaria and of kala-azar. My results showed that while the para-sites were easily found in the early cases, they became more and more scarce asthe disease advanced; until, in the old typical cases of malarial cachexia andkala-azar neither parasites nor pigment were to be found, even in blood takenfrom the spleen. I inferred then that kala-azar is probably only malaria, thoughit was possible that some secondary infection might account for the gravity ofthe cases. I also inferred - what no one would accept before then - that thespontaneous disappearance of the parasites must be due to the gradual estab-lishment of immunity; and that the low fever present in these old cases wasdue, not to the parasites, but to some secondary intoxication from the greatly


enlarged liver and spleen. And the same theories seemed to me to apply tokala-dukh.*

This investigation required repeated examination of the blood of all thecases which I could procure in the town; and, being made at high pressure,involved another estreme strain on the eyesight. Nevertheless I examinedseveral batches of dappled-winged mosquitoes fed on cases with parasites, butthe insects selected for the work were like some of those abounding at Calcut-ta, namely Anopheles rossi. All proved negative. My disappointment was con-siderable, but I was not satisfied that the feedings, which were left to assistants,were properly done. Many of the same insects caught in the houses of patientswere also negative. By the aid of my assistants, however, many fresh examplesof the law that the dappled-winged mosquitoes breed in pools of water on theground were obtained.

During my stay at Nowgong I wrote a short report, dated the 11th Oc-tober, on the infection of birds by the bites of mosquitoes46. This was notpublished until some months later; but of course the principal facts had longpreviously been published by Manson43.

At the conclusion of my work on kala-azar I returned, now utterly ex-hausted, to Calcutta.

20. Calcutta (November, 1898-February, 1899). The work confirmed. Arriving atCalcutta on the 19th November I set to work to pick up the threads of mywork on Proteosoma; to obtain cases of human malaria (the plague-scare hav-ing abated); and to write my report on kala-azar - this being a tedious businessrequiring a full discussion of many intricate details. But my health had nowsuffered greatly from the continuous exertion made under very trying cir-cumstances; and I felt scarcely able to complete even my report. The labour,the disappointments, even the successes, of the long and anxious investigationsof a single subject had been too much for me.

The cold and dry weather had now commenced in Calcutta; and the resultwas that the malaria parasites had become much more difficult to find, eitherin men or in birds. Added to this, as I had no room in my laboratory whichcould be warmed by a wood fire (a gas-stove injured the insects), the mos-quitoes could scarcely be persuaded to bite. And when they did so, it was ob-served that the parasites developed in them much more slowly than in hotweather.* It has just become highly probable that these diseases are due to a new parasite recentlydiscovered by Leishman and Donovan.

86 1 9 0 2 R . R O S S

Moreover, all this time I had failed to obtain any assistance in India, and sawno prospect of obtaining any. I had been told indeed by Manson that Dr. Da-niels was to arrive shortly; but he was being sent, not really to assist me, but toenquire into the correctness of my statements; and was to remain with meonly for a month or two. The only persons who had hitherto taken sufficientinterest in my proceedings even to look at my preparations (I mean from thebeginning of my work in 1895) had been Drs. Smyth, Maynard, Dyson, andCooke; and it was clear that no one really credited my results. Even the Di-rector General, who was then in Calcutta, would not visit my laboratory. Itwas the case of Galileo and the satellites of Jupiter over again!

I was, however, much cheered by the arrival of Dr. Rivenburg of the Amer-ican Mission, who, hearing of my work, came all the way from a distant partof Assam with his wife and children at his own expense to assist me. He hadbeen previously quite unknown to me; and I shall never forget his disinterest-ed action and the help he gave me.

I had also been delighted to hear from Manson that the work was now beingtaken up by Koch and the Italians. My papers had been published as described;copies of my Proteosoma Report42 had been sent to many persons interested inmalaria. On the 8th November Manson wrote again informing me that hehad just despatched some of my preparations to Rome, namely to Bignamiand Charles.

I did not become acquainted with the admirable work of Koch until later(section 23); but the efforts of Bignami and Grassi were now communicatedto me in a series of interesting and well instructed letters by Dr. EdmonstonCharles - a gentleman then staying in Rome, but whom I had never met, norcorresponded with before. From these and their own papers it was clear thatthe Italian writers had been inspired by my work and had been desperatelyendeavouring to follow it; that they had detected the genus (Anopheles) of mydappled-winged mosquitoes, and, after having seen my preparations, hadsucceeded at the end of November in finding my pigmented cells in an Italianspecies of this genus caught in infected houses. Bignami also claimed to haveinfected healthy persons by mosquitoes obtained in this manner; and, by alucky stroke, one of the persons bitten by some A. claviger was found to haveacquired the mild tertian parasite.

I shall return to this subject when describing the confirmations of my work.The efforts of Bignami and Grassi were, however, obviously hasty and un-reliable; while their writings were historically most inaccurate. They there-fore did not impress me, and exercised no influence whatever in the comple-


tion of my own labours. For several years afterwards, however, nearly all mywork was credited to these writers.

One interesting fact, however, I learnt from the Italians through Charles,namely that my grey mosquitoes belonged to the genus Culex and my dap-pled-winged mosquitoes to the genus Anopheles. Manson appears to havesent some of the former to Grassi, and, according to Charles’s letters of the19th November, he thought they were Culex pipiens - as a matter of fact theywere C. fatigans. Also from Charles’s letter of the 25th November and fromtheir own publications4 8 , 5 1 , it was clear that the Italians thought that my dap-pled-winged mosquitoes were Anopheles claviger; and in his letter of the 6thJanuary it was stated that Grassi considered some dappled-winged mosquitoeswhich I sent him were A. pictus - they were really A. rossi, Giles. I satisfiedmyself more fully next year at the British Museum regarding the zoologicalnames of the mosquitoes studied by me. The Italians had no difficulties in theserespects as they had Ficalbi’s works on gnats to guide them. They receivedsome more of my preparations, through Dr. Charles, early in January 1899.

On the 22nd December Dr. Daniels, of the Medical Service of British Gui-ana, arrived. Though somewhat sceptical at first, he was soon convinced afterseeing my preparations and repeating the experiments with care; and he fullyconfirmed my work in a paper, which however was not published by theRoyal Society until much later7 1. I am much indebted to him for his assistanceand advice in connection with my report on kala-azar - no one has a profound-er knowledge or a larger experience of malaria. In the time remaining to us weattempted several series of experiments on human malaria (cases now beingmore obtainable), mostly with the large brown dappled-winged mosquito ofCalcutta with which I had made most of my few but negative experimentsrecently in Calcutta and Assam. These too proved to be negative. We ascribedour failure to some mistake; but the cause was ill-fortune. The mosquitoeswere chiefly Anopheles rossi which in Bengal certainly do not easily take ma-laria.*

* It was, of course, the cold weather in Calcutta, but Daniels and I used incubators. Ste-phens and Christophers later obtained positive results in Nagpur with A. rossi, but onlyby very careful artificial regulation of the temperature71.

It should be clearly understood that all my experiments on human malaria since 1897were made under very unfavourable circumstances, and that I never considered my nega-tive results to be at all final.

At this time I informed Daniels of some other details; and, in view of a controversywhich arose later, he has kindly testified to this fact in the following letter:

88 1 9 0 2 R . R O S S

Several distinguished visitors came to us at this time, F. Plehn, A. E. Wrightand A. Ruffer. They all accepted our work, except the "black spores" men-tioned in section 17. Nevertheless Daniels and I did not think it right toabandon them without clear evidence; but when, later, I found closely similarbodies in large numbers in mosquitoes which had not been infected at all, myfaith was shaken; and it was disturbed still more when I failed to find them inthe infected mosquitoes of Sierra Leone. My doubts were mentioned in theconcluding sentences of my report on kala-azar.

That report was finished on the 30th January79, and contains eighty-oneclosely printed folio pages. My years’ special duty was now almost finished;but I could obtain no definite assurance from my chief that I was to be retainedon the same duty for an extended period. Yet the matter was vital to me.Nearly all the money at my disposal had been spent in consequence of theseresearches, chiefly because of the expenses connected with the constant changes

[footnote continued from p. 87]

Dear Ross,October 8th, 1900.

I shall have great pleasure in testifying to the following facts :(I) Shortly after my arrival in Calcutta in December, 1898, you showed me living

specimens of your "grey", "brindled", and "dappled-winged" mosquitoes.You pointed out to me the attitude assumed by the last, the position of its larvae in wa-

ter, and the peculiarities of its eggs.Since then I have learnt that these are characteristics of the genus Anopheles.You contrasted these with the eggs and larvae of other mosquitoes, which I now know

to belong to the genus Culex.(2) You showed me two species of "dappled-winged" mosquitoes, and I sent speci-

mens of them to the British Museum where they now are. They have been described byMajor Giles, I. M. S., as Anopheles.

You also showed me a specimen of a stomach of a mosquito with what are now knownas "zygotes". This you stated was the stomach of a "dappled-winged" mosquito, similarto those you had shown me, which had been fed on a patient with crescents in 1897.

(3) I may add that the development of Proteosoma, as demonstrated to me by you inthe "grey" mosquito, is essentially the same as the development of "crescents" in Anophe-les as observed by me in British Central Africa.

I am, Yours very truly,C.W.Daniels.

P.S. As regards breeding-places, you informed me that the "dappled-winged" mos-quitoes breed in puddles, the "brindled" mosquitoes generally in flower-pots, and the"grey" mosquitoes in tanks, ditches, etc.

Major R. Ross.C.W.Daniels.


of station to which my family and myself had been subject; and if I were nowcompelled to return to Secunderabad, I should not be able later to pay for mypassage to England. Moreover, both Daniels and Rivenburg were now leav-ing me, and it was evidently foolish to expect any further assistance in India-much more that of a trained entomologist, which I especially required for thecompletion of my work on human malaria. I therefore determined to leaveIndia forthwith and to return to England, trusting to fortune to give me anopportunity for finishing the investigation in a manner which I thought suit-able. I mention these personal details as I have been blamed for leaving Indiaat that moment.

Before doing so, I urged upon Government the importance of taking activemeasures for the prevention of malaria in accordance with my observations.Besides advising the strict use of mosquito-nets for a personal prophylaxis, Iurged especially a campaign against mosquitoes as the best measure for townsand cantonments, particularly against the dappled-winged mosquitoes, whichI said breed principally in water on the ground. My letter was publishedlater55, and I hope that the advice will soon begin to be taken.

I had also written a brief abstract of my work dated the 31st December,1898. This was presented by Laveran to the Académie de Médecine on the24th January, 1899, and was published soon afterwards55. In this paper myobligations to Manson and Laveran were acknowledged, I hope, in the fullmanner which honourable science demands. I wrote :

"Pour éviter tout commentaire erroné, qu’il me soit permis de déclarer icique mes travaux ont été entiérement dirigés par Manson, et que j’ai eu l’as-sistance de ses conseils et de son influence à toute occasion; je dois aussi re-mercier le Dr. Laveran de m’avoir envoyé ses avis si autorisés. Quand, en maidernier, je lui envoyai des spécimens de mes corps pigmentés du moustique,il reconnut immédiatement la vraie nature de ces éléments."

And I added in conclusion,"Je considère comme probable que la malaria est communiquée á l’hommeuniquement par les morsures des moustiques et peut-être d’autres insectes."

21. England (March-July, 1899). Foundation of the Liverpool School of TropicalMedicine. On the voyage to England (February 1899) I had full time to con-sider the present condition of our knowledge about malaria, especially in rela-tion to the all-important subject of prevention. It was almost certain that in-fection is caused solely by the bites of insects - but of what insects only? My long

90 1 9 0 2 R . R O S S

negative work had almost proved that the commonest Indian mosquitoes, thegrey and brindled genera, do not carry aestivo-autumnal infection, at least. Onthe other hand, it was certain that two species of dappled-winged mosquitoesin Secunderabad, and one species in Rome, do carry it; while, if Bignami’sobservation was to be trusted, the last species carries also the mild tertian infec-tion. But Secunderabad and Rome are not the whole world; even in Bengal,Daniels and I had not succeeded in infecting dappled-winged mosquitoes. Thequestion as to which species do or do not carry malaria might prove to be avery complex one, not to be solved only by a few local experiences; thereare probably hundreds of species of mosquitoes in the world, each of whichwould have to be tested unless we could find some good reason for limitingthe enquiry. I therefore sought for some such reason, and found one. For cen-turies it had been known that malaria is connected with stagnant water on theground - not with water in the pots, tubs, and tanks which abound close to allhabitations, but with marshes and pools on the surface of the earth. Againmalaria was known to increase every year at the rainy season, and subsoil-drainage was known to mitigate if not remove the disease. Hence it was ex-tremely probable that the insects which carry malaria breed only, or chiefly, in terrestialwater. For years we had assumed that the disease is caused by organisms whichspring from marshes. We had been partially right, but not wholly right; it isnot the infective but the infecting organism which springs from the marsh -not the germ but the carrier of the germ. Now, referring to mosquitoes alone,which varieties of these insects breed only or chiefly in terrestial waters? I re-membered my frequent observations on this point (sections 14, 15, and 19).The grey and brindled mosquitoes breed chiefly in tubs and pots in India; butthe dappled-winged mosquitoes breed in pools on the ground. Now it was only theselast which, hitherto, had certainly been connected experimentally with ma-laria.*

What a weapon for good was now placed in our hands! Hitherto when wewished to remove malaria we were obliged to drain a whole area, recognizingonly that all terrestial waters seemed to be dangerous. Now we should be ableto go to a place and to point out the actual pools which cause the disease, byshowing that they contain the larvae of the culpable insects. The expense ofdealing only with these would be much less.

Shortly after my arrival in England in March I learnt something about thezoological classification of mosquitoes from Mr. E. E. Austen of the British* This reasoning was by no means obvious or even known until after our work at SierraLeone. In temperate climates grey mosquitoes (Culex) also breed often in terrestial water.


Museum. I found that, as I had already partially learnt through Charles, mydappled-winged mosquitoes were those of Meigen’s genus Anopheles and thatboth my grey and brindled mosquitoes belonged to the same genus, namelyCulex. I was dissatisfied with this because it seemed to me certain that theywere of different genera. Recently Theobald in his fine work on mosquitoes75

has separated them, placing the brindled mosquitoes in the genus Stegomyia,and reserving the name Culex for the grey mosquitoes. Later, Giles deter-mined that the grey mosquitoes which carry Proteosoma are Culex fatigans, andcalled the large negative dappled-winged mosquitoes of Calcutta Anophelesrossi.*

Meanwhile Manson had been urging his great scheme of creating specialschools for the teaching of tropical medicine, and had now received the sup-port of Mr. Chamberlain. In Liverpool, Sir Alfred Jones, supported by Pro-fessor Boyce of University College, Mr. Adamson, Chairman of the RoyalSouthern Hospital, and many other gentlemen, had warmly taken up thescheme, and now appointed me the first lecturer of the Liverpool School ofTropical Medicine. I therefore found myself no longer an isolated worker, buta member of a company determined to advance the interests of life and healthin the tropics. And it was an auspicious moment; for the great weapon whichhad just been forged for the prevention of the most important of tropicaldiseases needed strong hands to lift and wield it.

Almost my first care on returning to England was to consult eminent zool-ogists regarding the proper nomenclature for use in connection with the de-velopmental stages of the parasites in mosquitoes. With the aid of ProfessorHerdman I published a paper on the subject59, in which, abandoning the hastyprovisional nomenclature hitherto used by me, I called the motile filaments,microgametes; the pigmented cells, zygotes; and the thread-like bodies, blasts.I also suggested a classification for the parasites of men and of birds. But thereis still great divergence of opinion on these subjects.

Evidently West Africa, a rich and enormous country hitherto paralysed bymalaria, was destined to be the first objective. I lost no time in urging the ad-visability of sending me there in order to complete my studies of the diseaseand determine its agents on the spot. In July I delivered my inaugural lectureand demanded attention for my scheme for extirpating malaria by attackingthe pool-breeding mosquitoes5 8. At the end of July 1899, accompanied byMr. E. E. Austen of the British Museum and Dr. H. E. Annet, Demonstrator* Owing to an error he thought that it was this kind in which I had first found the pig-mented cells in 1897.

92 1 9 0 2 R . R O S S

of the Liverpool School of Tropical Medicine, I left England for Freetown,Sierra Leone.

22. Sierra Leone (August-September, 1899). The investigation completed. Wehave now reached the last chapter of this history - which I fear has becometedious. If a literary simile may be allowed in a scientific narrative, I had atlast come to my Ithaca, after many mischances sent by many opposing deities.Two years had elapsed since I had seen the pigmented cells of the human para-sites - two years of fruitless efforts, interruptions and bad fortune; and sevenyears had elapsed since I had commenced the special study of malaria; but nowassisted by my able colleagues and myself, I needed but a week or two to dem-onstrate all the stages of the human parasites in dappled-winged mosquitoes,and also to ascertain the fundamental principles upon which State sanitationagainst tropical malaria should be based. I will be brief; the details are given inthe publications60,67.

On the day after landing (10th August) we found two species of dappled-winged mosquitoes (Anopheles costalis, Loew, and Anopheles funestus, Giles) inabundance. On the 13th August, we detected a pigmented cell, evidently ofthe mild tertian parasite, in one of them. A few days later, in some barracksthere was much malaria, we ascertained that a quarter of the mosquitoes (al-most exclusively A. costalis) were infected; and found in them pigmented cellsevidently derived from all three varieties of parasites - quartan, tertian andaestivo-autumnal. We also made a few formal feeding experiments, and couldhave made as many more as we pleased. The material was unlimited; but ourtime was short, and the proof was already sufficient.

We then investigated the conditions under which the Anopheles breed andpropagate malaria. It was the rainy season and the place was full of stagnantpools. Everywhere the larvae of the dappled-winged mosquitoes were in thesepools, while those of the grey and brindled mosquitoes occurred in tubs andpots. The great law of malaria - its connection with stagnant water on theground - was explained. Moreover, simply by noting the presence of the lar-vae, we could tell at a glance which pools were dangerous to health and shouldbe dealt with in the public interests.

The habits of the insects were noted and found to be precisely similar tothose of the Indian species. We studied particularly the characteristic attitudeof the larvae and adults of the dappled-winged mosquitoes, as formerly ob-served in India - invaluable tests for the immediate and easy recognition of theagents of the disease; we noted the evidence demonstrating the short flight of


the insects, and their connection with rank tropical vegetation; we disposed ofthe ideas that tidal swamps cause malaria, but showed how earth-works pro-duce outbreaks by the formation of pools of rainwater. In fact we were able togive a thorough explanation of the manner in which the old paludic and tel-luric theories of malaria originated.

We were also able to establish for the first time the fundamental principleswhich the State must adopt in order to extirpate malaria in tropical cities.These are (1) scrupulous drainage of the soil; (2) pending this, the persistenttreatment of Anopheles’ breeding-pools by culicicides; (3) the segregation ofEuropeans. We also recommended the protection of public buildings, suchas barracks, gaols, hospitals, and rest-houses by wire gauze screens; the isola-tion of the sick; and the habitual employment of mosquito-nets and punkahsby individuals.

Our results and recommendations were immediately communicated toGovernment and also published in the medical press60.

After our return to England in October we published a full report of ourexperiences 6 7. In this book, written by myself and endorsed by my colleagues,I collected the principal results of all my researches on malaria made duringseven years; and illustrated the life-history both of the human and avian para-sites in mosquitoes by numerous photo-micrographs made by myself. Thiswork, therefore, which records the completion of these labours by the success-ful demonstration of the whole evolution of the human parasites in Anopheles,constitutes the summary and conclusion of all my previous papers. It has beensaid that the book was based on the writings of those who, as a matter of fact,learnt everything from me; but I can say with exact truth that if no one exceptMacCallum and Koch had touched the subject since 1895, scarcely a word inthe Report would have been different.

It should be added that in March 1900 I gave an abstract of the history ofmy work in a lecture at the Royal Institution68; and particularly, that towardthe end of the same year the President of the Royal Society, Lord Lister, for-mally accepted my results in his Address to the Society.

From this time my own efforts have been devoted almost entirely to thepractical campaign against malaria. Few people are aware of the fact that eventhe most solid discoveries of science may be allowed by the public to remainquite disused and inoperative unless strenuous efforts are made to urge themupon the popular attention. Even yet, in spite of the constant endeavours ofmany persons, very little has really been done towards the extirpation of mala-ria. This has been principally due to the fact that, for some inexplicable reason

94 1 9 0 2 R . R O S S

which wholly escapes me, the chief prophylactic measure recommended byme, namely a campaign against mosquitoes by drainage and petrolage, hasbeen generally held to be impossible; yet it is the only general prophylacticmeasure possible in tropical towns. The struggle over this matter has been al-most as severe as that over the original problem; but it is now drawing to aclose. It is impossible to discuss the matter here. Suffice it to say that in the twoprincipal towns, Havana and Ismailia, in which the measure has been ade-quately employed, the reduction of malaria has already been as much as eightyper cent.

This then is the conclusion of the history. I fear that some of the personaldetails may have appeared out of place in the narrative; but they have beenintroduced - though unwillingly - for a special reason. No form of enterpriseis of such transcendent importance to humanity in general as the investigationof disease - the principal enemy of every man. The interests of all nations, notonly in the present but in the future, demand that every possible encourage-ment should be given to such investigations - particularly that medical men,who are in an excellent position to undertake them, shall receive the warmestassistance in their self-imposed task. The story, however, which I have felt it aduty to record in this lecture adds but one to the many instances of medicalhistory which show that little attention is given to this point. My labours willbe abundantly repaid if earnest students in this field of science receive, in thefuture, in consequence of this narrative, a little more assistance than was givento me.

23. Confirmation and extensions. It is impossible for me to describe here, even indetail, the vast amount of work which has been done in many parts of theworld on the mosquito theory of malaria since 1899; but it is necessary just totouch upon some of the more immediate verifications of my observations.

(1) Undoubtedly the first verification was due to Koch and his assist-ants63,64. Professor Koch was kind enough to communicate to me at my re-quest, in a letter dated the 15th May 1901, the origin and progress of his re-searches on the mosquito theory of malaria. He says:

"The idea that mosquitoes may be the cause of malarial infection occurredto me on my first visit to the tropics in British India in the winter of 1883-1884,and since then I have always spoken in this sense in my lectures and to my as-sistants. I have not indeed myself published anything about these views; butyou will find a notice in R. Pfeiffer’s work Beiträge Zur Protozoen-Forschung,Berlin, 1892 (near the end).


"The fact that malaria, when it occurs epidemically, is often confined al-most entirely to the children, the adults remaining free and therefore havingbecome immune, I discovered first in villages in Java which lie in the valley ofAmbarawa. That was at the beginning of November 1899. I reported on it onthe 9th of December 1899, and my letter was published in the Deutsche Medi-zinische Wochenschrift, No. 5, 1900, beginning of February. I obtained my first,successful cultivation of Proteosoma in mosquitoes in company of Prof. R.Pfeiffer in Rome in September 1898. We continued the investigation in Ber-lin; and in the middle of November we followed the developmental stages ofthe parasite up to the sickle-shaped bodies in the poison glands of the mosqui-to - that is up to the end. We were able to determine the form of Würmchen(vermicule) in Proteosoma so easily because I, with Professor Kossel, had al-ready in June of the same year (1898), without knowledge of MacCallum’sinvestigation, detected the origin of the spermatozoa, the process of fertiliza-tion, and the formation of the Würmchen in Halteridium.

"The publication of this investigation was very much delayed in conse-quence of the long time taken for the reproduction of the photographs in away which satisfied me.

"At all events I have not thought it necessary to attempt to assert my priorityon this occasion as the matter concerned only the confirmation of alreadyknown things."

Professor Koch has the honour of having been one of the first, not only in-dependently to conceive the mosquito theory of malaria, but also to attack itby experiment. He and Kossel independently observed the function of themotile filaments by the employment of correct methods of staining: this ispractically admitted by Bignami (Lancet, 2 (1898), p. 1898) who was later able,probably through his instruction, to demonstrate the chromatin in the motilefilaments50 - a thing which he had refused to credit before. Koch also was thefirst to fill a gap in my own researches on Proteosoma by demonstrating thepassage of the vermicule through the wall of the mosquito’s stomach - a sub-ject in which Grassi merely followed him later. That he succeeded in culti-vating Proteosoma in Rome and Berlin, in September to November, 1898,shows that he was the first to confirm my own observations. About that timeDr. Annett of the Liverpool School of Tropical Medicine saw some of his prep-arations of pigmented cells in Berlin. Koch’s discovery of the frequent infec-tion in native children in the tropics was one which I had entirely failed tomake - although I should have made it; and is an addition to our knowledge ofthe very highest importance, being of far greater intrinsic value than much of

96 1 9 0 2 R . R O S S

the trifling matter which has been put forward in other quarters with muchréclame. It enables us to explain with ease the source of most malarial infectionsin the tropics, and, besides, gives a complete revelation regarding the possibil-ity of immunity in malaria, a thing in which no one would previously believe.Added to this Professor Koch has pressed still further onwards, and pushedwith authority and ability the great subject of the practical prevention of thedisease in the tropics - a matter the importance of which few writers on thesubject have seemed able to comprehend. The methods recommended by meconsist principally of the use of mosquito-nets and the extirpation of mosqui-toes; but Koch at once inaugurated a new conception which had not occurredto me and which consisted in the cinchonization of the people in malariouslocalities. Although this measure is not always possible in its full extent, stillexperience shows that in a modified form it is most useful; and I have come tothe conclusion that it should always be enforced as much as practicable in addi-tion to the measures which I advocate. It was also Koch who was the first tocall general attention to the important fact that a sudden and ill-advised doseof quinine is apt to precipitate attacks of blackwater fever in certain personsand localities.*

(2). Many erroneous ideas have been formed about the Italian work (re-ferred to in section 20) by those who have no practical knowledge of malariaor full acquaintance with the literature. The facts are exactly as follows.

The South of Italy affords unparalleled advantages for the study of malaria,because abundance of material is there combined with great facilities in connec-tion with laboratories, literature, and scientific communion; hence, though theprincipal discoveries have been made elsewhere, the writers of Southern Italyhave been able to add to them much detail, which has proved more or lesscorrect. It was hoped after Laveran’s discovery that they would be able to findthe extracorporeal phase of the parasite; but, unfortunately, misled by fond-ness for hypotheses, they fell into fundamental errors. Most of them hastilyconcluded that the motile filaments are "agony-forms"; and, as described insections 6 and 11, A. Bignami rejected Manson’s induction on this account;and another writer, G.B. Grassi, abandoned the whole mosquito theory (1)because mosquitoes do not bite birds, (2) because they abound in places wherethere is no malaria, and (3) because the malaria parasites die in the stomachsof mosquitoes. At the same time he maintained that the extracorporeal stage

* I should like to add, in contradiction of many inaccurate statements which have beenmade, that his acknowledgment of my own observations has been the most completepossible.


of the parasite is a free-living amoeba 10. Bignami however, while rejectingManson’s version of the theory, adopted King’s, and stated that he had evenmade some experiments on the subject in 1894; but these were only referred toas a past event29, and seemed to have been quickly abandoned.

It is probable that these writers would have remained indefinitely in thisposition but for the researches of others. In 1895-1897, Sacharoff23, Simond35,MacCallum 36, and myself32 destroyed the Italian theory regarding the motilefilaments; and then the publications of the 18th December, 189738, the 26thFebruary, 1898 39, the 21st May42, the 18th June4I, the 24th September43, and11th October46, completely demonstrated the life-history of this group of para-sites in mosquitoes; clearly indicated the genus concerned in the propagationof aestivo-autumnal fever; and gave other details mentioned in section 17.

As all these papers, except those of the 21st May and the 11th October(which were in fact covered by Manson’s papers of the 18th June and the 24thSeptember), were published in such a prominent organ as the British MedicalJournal, it is to be assumed that they were from the first known to the Italianwriters, who have always shown a prompt knowledge of the labours of others.In his first publication44, Grassi refers to my work without mentioning myname or giving references - as if it were then perfectly well-known in Italy.The later publications of Bignami and Grassi48,47 show that they were quiteintimate with it before they themselves attained any definite results.

Such being the case, in order to follow my work in Italy and elsewhere, allthat was now needed was to determine the genera of my grey and dappled-winged mosquitoes from such indications as I had been able to give. The for-mer had been described in two papers, and was most evidently closely allied toCulex pipiens; and the latter, in which the aestivo-autumnal parasites had beenshown to develop, were described in 189738 as follows:

"The latter are a large brown species biting well in the day-time, and in-cidentally found to be capable of harbouring the filaria sanguinis hominis. Theback of the thorax and abdomen is a light fawn colour; the lower surface ofthe same, and the terminal segments of the body a dark chocolate brown. Thewings are light brown to white, and have four dark spots on the anterior ner-vure. The haustellum and tarsi are brindled dark and light brown. The eggs -at least when not properly developed - are shaped curiously like ancient boatswith raised stem and prow, and have lines radiating from the concave borderlike banks of oars - so far as I have seen, a unique shape for mosquito’s eggs.The species appears to belong to a family distinct from the ordinary brindledand grey insects; but there is an allied species here, only more slender, whiter,

98 1 9 0 2 R . R O SS

and much less voracious." In the next paper39 these small insects also are called"dappled-winged".

At that time in Italy the Culicidae had been carefully studied by Ficalbi inseveral works31 , and it was an easy task for anyone possessing these works, andalso having fresh mosquitoes for dissection, to determine the genus of mydappled-winged mosquitoes from my description alone. Although I did notgive the entomological criterion of the genus Anopheles (the long palpi of thefemale), I gave three other details which sufficed for the identification. First,the dappled-winged mosquitoes belonged to a group distinct from the greymosquitoes (Culex pipiens type). Secondly, both species of this group hadspotted wings ; and still more particularly, one of them (certainly) had exactly"our dark spots on the anterior nervure". Now it is well-known that veryfew Culices and Stegomyiae have spotted wings, while Anopheles almost alwayshave them. The Anopheles, however, not only generally possess spotted wings,but the spots are generally four in number and arranged along or close to the anteriornervure. Lastly, if any doubt remained the observer would only have to catchthe first spotted-winged female gnat and to examine the eggs within her, whenthey would be immediately seen to possess the characteristic boat-like shape,with the well-known clasping membrane simulating oars on either side.

It is curious that some of those who have written on the subject have over-looked the fact that the very first Italian mosquito which from its name alonewould be suggested by my description was Anopheles claviger. Two of thesynonyms of this insect are Anopheles quadrimaculatus, Say, and Anopheles ma-culipennis, Meigen!

There is, however, no doubt whatever that the Italians detected the genusof my dappled-winged mosquitoes, because they themselves say so in two oftheir articles of November48,51 . Nuttall admits the fact74. But there is reasonto suppose that they recognized the insects long before November.

It was evidently Manson’s paper of the 18th June, 1898 which stimulatedthe Italians to renewed activity, because they set to work shortly afterwards.But their success was delayed by efforts towards originality. Grassi endeav-oured to find the guilty species of mosquito by its prevalence in malariouslocalities. His efforts were a close repetition of mine in the Sigur Ghat - evenhis servant was attacked by malaria as mine had been. He discovered threespecies of guilty mosquito, namely Culex penicillaris, C. malariae (so named byhim - really C. vexans), and Anopheles claviger - principally (per lo meno) thefirst44. I have already shown in sections 11 and 12 how useless it is to attemptto identify the malaria-bearing species by its preponderance in malarious


places; and it has now been demonstrated that even in Italy there is no such rela-tion between the disease and its agent. Anopheles abound where there is nomalaria - even round Liverpool. Needless to say then, two out of the threespecies isolated by Grassi have nothing to do with the disease. He was rightregarding the third, A. claviger; but it is quite reasonable to suppose that hedetached this simply from my description of the dappled-winged mosquitoes.As a matter of fact all these epidemiological efforts of Grassi, though interest-ing in a small way, were nothing but a series of vague speculations.*

Meantime Bignami, after four year’s inaction, had returned to his old meth-od of attempting to infect men by the bites of mosquitoes brought from mala-rious places. His results are minutely recorded in his paper48. He set to work inAugust - that is, after Manson had proclaimed at the British Medical Associa-tion that I had succeeded in infecting birds by the bites of mosquitoes 43. Big-nami’s task was now vastly simplified; with the guidance of my work hecollected his mosquitoes from infected houses; whereas if he had continued toact in accordance with his own theory he would have collected them frommarshes - which would have led to constant failure (section 13). He claimedhis first success early in November, but still could not say which of the variouskinds of mosquitoes employed by him had produced the result.**

Up to November therefore the Italians had failed either to find the guiltyspecies of mosquito or to demonstrate the life-cycle of the parasite in the in-sects. At this point Charles’s series of eight letters addressed from Rome to me(dated from the 4th November to the 14th January) commence. They havebeen printed by me with his consent; and show clearly (what however can bealso demonstrated from their own writings) that the Italians were then inti-mately acquainted with my work; that they had received my report42 givingfull details of technique: and that they had detected the genus of my grey mos-quitoes (from specimens sent by Manson) and of my dappled-winged mos-quitoes (from my description). In his letter of the 8th November, 1898, Man-

* The writers of some zoological text-books, who have evidently had little personal ex-perience of the disease, seem to have actually believed that Grassi determined the "Ano-pheles malariferi" by these efforts. That is not the case. In an early work54 I said that theywere made independently of Manson and myself; but this was written before I studiedthe Italian work with close attention; and since then I have withdrawn the statement72.** That human malaria is conveyed by the bites of mosquitoes had of course been proved- practically to a certainty - by my infection of numerous birds three months previously.Bignami’s experiment was merely a formality of which the success could already be fore-told with confidence. The statement, frequently made, that he was the first to give exper-imental demonstration of this fact may be set aside without comment.

100 1 9 0 2 R . R O S S

son records having sent some of my preparations to Charles and Bignami (onor before that date); and Charles in his letter of the 25th November recordsshowing one of these to Grassi (on or before that date). It is possible, however,that the Italians had seen my preparations long before this, as numbers of themhad been sent to Manson and Laveran in the spring and summer; and they mayalso have seen those of Koch, who had cultivated Proteosoma in Rome in Sep-tember.

Bignami, Bastianelli, and Grassi had now evidently determined to resort tothe correct method for determining the guilty species of mosquito, and imi-tated exactly the experiment by which I had ascertained the second host ofProteosoma in the previous March. The experiment was recorded by them onthe 28th November51. They fed six Culex pipiens, one Anopheles nigripes andfour Anopheles claviger on some cases of crescents, and at last found my pig-mented cells in two of the last species. They do not record the exact date onwhich this observation was made, but from Charles’s letters it would appearto have been on the 25th November or later.

This, if correct, was the first definite demonstration of the guilty species ofmosquito in Italy. It was made fifteen months after my original demonstrationof the same parasite in the same genus of mosquitoes in Secunderabad on the20th August, 189738, and nearly four months after Manson had announced thewhole life-cycle of Proteosoma at the British Medical Association43. The Italianexperiment was, however, of doubtful correctness, because the authors do notstate that the mosquitoes used by them had been bred from the larvae51. At thesame time they actually impute to me the very fault which they themselveswere committing, and do so contrary to the printed evidence of my ownwords.*

In their next paper53 they claim to have found the various developmentalstages of the aestivo-autumnal parasites in A. claviger caught in houses andstables, or fed on patients in hospital. Here again, examination of the publica-tion shows that none of the insects employed seem to have been bred from thelarvae; and, what is still more important, the number of insects on which theobservations were made is not exactly given. For all we know, the wholepaper may have been written on the strength of only a very few positive re-sults; and this is the more possible because it describes a life-cycle which is an

* They say that my experiment was doubtful because my mosquitoes may have previ-ously bitten other animals51. Now it is clearly stated in my publications* that the insectsused by me had been bred in "bottles from the larvae"; and from the whole tenor of myresearches it was evident that such was the case.


exact repetition of that of Proteosoma. The authors give no precise differentialexperiments in order to prove the connection between the pigmented cellsseen by them and the haematozoa. For this proof they rely upon my Proteosomareport42, to which, however, they scarcely refer. Although their paper givesto the ignorant the impression of being original, it is in reality merely a re-script of mine.

Meanwhile Bignami and Bastianelli had been continuing their attempts toinfect men by A. claviger taken from houses; and claimed a second positive re-sult early in December. In this case, however, by good fortune, the infectionproved to be a mild tertian one. Some months later, these two authors pub-lished a paper56 recording the development of this parasite also in Anopheles.This was the first, and, indeed, only important Italian result which had notbeen previously indicated by me; I had made no observation connecting thetertian parasite also with the dappled-winged mosquitoes.

Subsequently the same authors and Grassi claimed to have demonstratedthe development of the parasites in Anopheles nigripes, A. bifurcatus, and A. su-perpictus.

They also claimed to have shown that the members of the old genus Culexdo not carry malaria; but this had long previously been abundantly proved byme in India, at least with regard to the aestivo-autumnal parasite; and the factis that Grassi had only identified my grey mosquitoes, which I had shown tobe negative to this parasite. Their first drawings of the parasites in mosquitoeswere not published until the spring.*

In my first reference to the Italian work I accepted it with some reserve; butafter a careful examination of their writings made in 1900 I felt much morescepticism. Their work during the winter of 1898-1899 is evidently hasty anddeficient in exact details regarding the various observations; and the generaltenor of their historical passages is so inaccurate as to inspire grave doubts re-garding the whole literature. I think that at that time they found my pigment-ed cells in a few, possibly a very few, A. claviger and that Bignami and Bastia-nelli also showed that the tertian parasite develops in the same insects; butbeyond this it is impossible to speak with confidence. Many of their detailsalso are derived from me.

My work was completed in the autumn of 1899 at Sierra Leone (section22) and was published immediately6 0. Many of the details are incorporated in

* For an independent account of all these researches the detailed history of Nuttall 65 andespecially his critique on the priority question74, should be consulted.

See also72,73,76.

102 1 9 0 2 R . R O S S

Grassi’s book published in June next year69. This work, which is dedicated toManson, is principally a compilation of the researches of others - the historicalpassages being quite inaccurate. At the bottom of page 31 of the first edition,the author says, "Giova infine far risaltare the io arrivai agli Anopheles mala-riferi independentemente da Ross, le cui ricerche sui parassiti malarici degliuccelli furono pubblicate quasi contemporaneamente alla mia prima Notapreliminare." He and his colleagues found the "Anopheles malariferi" in Italyby detecting the genus of my dappled-winged mosquitoes; but they did notincriminate it with certainty until the end of November, five months afterManson published my work on the malaria of birds41. Grassi’s "first prelimi-nary note"44 was published more than three months after this paper of Man-son’s, and, moreover, refers to my work as a well-known matter even then. Ifound the "Anopheles malariferi" in two species of mosquito in India fifteenmonths before Bastianelli, Bignami, and Grassi found it in Italy. Speakingquite strictly and accurately it is the principal merit of Grassi to have discov-ered, not the "Anopheles malariferi", but its correct entomological name.*

Excepting the discovery of the host of the tertian and perhaps the quartanparasites, the Italian work was simply a local affair, done, like the work of mycolleagues and myself in Sierra Leone and of other observers in many parts ofthe world, on the basis of my Indian researches culminating in July 1898 (sec-tion 17).

Of the sixteen and more species of Anopheles which have now been definite-ly connected with malaria, only three or four were incriminated by the Ital-ians; it is therefore quite incorrect to attribute the determination of this rela-tion to them - much more to attribute it, as some have done, to Grassi alone.The connection between Anopheles and malaria has been determined by theunited efforts of many observers in many parts of the world.

*Early in 1903 this writer published a pamphlet purporting to be a translation of impor-tant papers on the subject (Documenti riguardanti la storia della scoperta del mode di transmis-sione della malaria umana; Milano). It contains no bibliography nor accurate history of theevents; and omits most of the principal publications of my work. It purports to give infull my paper recording the original discovery of the pigmented cells38; but on exam-ining this copy I find that the drawings of the cells given by Manson, and the remarks ofManson, Bland Sutton, and Thin (all of which, of course, absolutely establish the genu-ineness of the discovery) are omitted without the smallest explanation. The author thenproceeds to claim the discovery for himself. This work also is dedicated to Manson - a factwhich may lead many to believe in its accuracy; but Manson has publicly stated that itwas dedicated to him without his permission (Lancet and British Medical ]ournal, 28thMarch, 1903).


(3) Certainly not less important than the Italian work has been that of theMalaria Commission of the Royal Society, consisting of Drs. Daniels, Steph-ens, and Christophers. After confirming my results in Calcutta as mentionedin section 20, Dr. Daniels proceeded to British Central Africa, where he metDrs. Christophers and Stephens, who had proceeded there after a month’s stayin Italy in the autumn. These observers had great trouble at first in obtainingsuitable cases for experiment, but finally succeeded in doing so. Daniels con-firmed our results in Sierra Leone, and added many useful and interesting de-tails. Stephens and Christophers afterwards followed us in Sierra Leone andelsewhere in West Africa, and then proceeded to India.

The researches of all these gentlemen are given in the admirable reports tothe Malaria Committee of the Royal Society 7 1. These researches have had theeffect of completely consolidating previous work on the subject. The authorshave shown no less than eight species of Anopheles to be amenable to the ma-laria infection, and that Culices and Stegomyiae are always refractory; theyhave demonstrated many of the habits of these insects in various parts of theworld; and, besides, have given us much invaluable information regardingthe pathology of the disease, especially of blackwater fever. Stephens andChristophers also found independently the great law of Koch regarding theprevalence of malaria amongst native children in the tropics.

The perusal of the writings of these gentlemen and of many other observerswill convince any one that it is impossible to do justice to them in the form of abrief review; it is scarcely even fair to attempt to describe such laboriouswork in a few words; and I shall therefore now draw this lecture to a closewith the remark, that I hope soon to deal with all these investigations in amanner which is due to them. But I should like to conclude with the names ofa few of those who have more recently added valuable information to ourstore of knowledge regarding the mosquito theory of malaria - particularlyZiemann, Manson, T. Manson, the members of the numerous expeditions ofthe Liverpool School of Tropical Medicine (Drs. Fielding-Ould, Annett,Dutton, Elliott, Logan Taylor), Fernside, James, Low, Sambon, Van derScheer, Van Berlekom, Celli, Nuttall, Shipley, Ruge, Howard, Theobald,Schaudinn, and Sir William MacGregor. I omit to refer to their works, andthose of many others, only because it is impossible to do so properly withinthe limits of this work.

It would not be right, however, to conclude without referring to those mostconspicuous examples of the success of anti-malaria measures for the improve-ment of public health - the cases of Havana and Ismailia. A campaign against

104 1 9 0 2 R . R O S S

yellow fever and malaria was commenced at Havana early in 1901; and Colo-nel and Assistant Surgeon General Gorgas of the United States Army, whowas in charge of the work, has recently reported as follows on the success of it,in a lecture delivered on May 22nd at the New York Post Graduate ClinicalSociety.

"The results of these combined measures were very marked. Mosquitoesentirely disappeared from many parts of the city, and were decreased every-where. On the first inspection made in January, 1901, 26,000 collections offresh water were found in the city, containing mosquito larvae, this exclusiveof the cess-pools. In January 1902, the consolidated inspection reports cover-ing the same area, showed less than 300; but the most striking evidence was itsresults on yellow fever. It must be borne in mind that yellow fever had beenconstantly in Havana since 1760, that it was not, as it had been in our NorthAmerican cities, some years present and some years absent, but steadily everyyear and every month and every day, in all that time. The deaths from yellowfever had been since 1889, about as follows: 303 (1890); 364 (1891); 352(1892); 482 (1893); 388 (1894); 549 (1895); 1355 (1896); 743 (1897); 127(1898); 118 (1899); 301 (1900) ; in 1901, the first year of our mosquito work5, and since September 1901, not a single case.

The work with regard to malaria is not quite so striking, and this necessarilyfollows from the nature of the disease. But I think the results, as shown by the

Table 2. Statistics of malaria at Ismailia.*


sanitary reports, are very hopeful, with regard to malaria, and indicate that inthe course of time, malaria can be also eradicated. In 1900, the year before mos-quito work, the deaths from malaria were 344; in 1901, the first year of mos-quito work, they had fallen to 151; in 1902, the second year of mosquitowork, they had dropped to 90, and, for the first four months of 1903, 16."

At the end of 1902, the Suez Canal Company asked me to go to Ismailia onthe Suez Canal, in order to advise regarding the best measures to take againstthe malaria which had long been prevalent in that town. I advised active oper-ations against the mosquitoes; and this advice was followed with great ener-gy and success. The table of statistics (Table 2), kindly supplied by PrinceD’Arenberg, the President of the Company, speaks for itself.

Not only, however, from this place do we hear of reduction of sickness andmortality. Undoubtedly the whole West Coast of Africa is much improved,and good accounts continue to flow in from Lagos, the Gold Coast, BritishCentral Africa, Hongkong, and further India; and it is to be hoped that withina few years malaria will, as Sir William MacGregor says, have lost its terrors,at least for Europeans who are called upon to serve in the tropics.

This list of works, chronologically arranged, includes chiefly my own writings, many ofwhich are omitted in bibliographies, and such others as are referred to in the text.

1. Manson, On the Development of Filaria Sanguinis Hominis and on the Mosquito Consid-ered as a Nurse, Linnean Society, 1878. Also Trans. Pathol. Soc., 32 (1881).

2. King, "Insects and disease, mosquitoes and malaria.", Popular Sci. Monthly, Sep.(1883).

3. Laveran, Traité des Fièvres Palustres, Paris, 1884, p. 457.4. Celli and Marchiafava, Fortschr. Med., (1885).5. Macloskie, "The poison apparatus of the mosquito.", Am. Naturalist, 1888.6. Lewis, Physiological and Pathological Researches, Lewis Mem. Comm., London, 1888,

p. 638.7. Agenore, "Acqua potabile e malaria.", Atti Accad. Med. Roma, 5 (1890).8. Marino, "Dell’ acqua dei luoghi malarici.", Riforma Med., (1890).9. Grassi and Feletti, Several papers, Zentr. Bakteriol., 9 (1891).

10. Grassi and Feletti, "Contribuzione allo studio dei parassiti malarici.", Atti Accad. Gioe-nia Sci. Nat. Catania, 5, Ser. 4a.

11. Laveran, Du Paludisme et de son Hématozoaire, Paris, 1891, p. 147.12. Ross, "Fever with intestinal lesions.", Trans. South Indian Branch, Brit. Med. Assoc.,

1892.13. Ross, "Cases of febricula with abdominal tenderness.", Indian Med. Gaz., (1892) 166.

106 1 9 0 2 R . R O S S

14. Ross, "Entero-septic fevers.", Indian Med. Gaz., (1892) 230.15. Ross, "A study of Indian fevers.", Indian Med. Gaz., (1892) 290.16. Ross, "Some observations on haematozoic theories of malaria.", Med. Reporter (after-

wards Indian Lancet), (1893) 65.17. Ross, "Nodulated and vacuolated corpuscles.", Indian Med. Record, (1893) 213.18. Ross, "Solution of corpuscles mistaken for parasites.", Indian Med. Record, (1893) 310.19. Smith and Kilborne, Investigations into the Nature, Causation and Prevention of Texas or

Southern Cattle Fever, Bull. No. 1, Bur. Animal Ind., U.S. Dept. Agr., 1893. Also seeZentr. Bakteriol., (1893).

20. Ross, "Third element of the blood and the malaria parasite.", Indian Med. Gaz., Jan.(1894) 5.

21. Ross, "A list of natural appearances in the blood which have been mistaken for formsof the malaria parasite.", Indian Med. Gaz., Dec. (1894) 441.

22. Manson, "On the nature and significance of the crescentic and flagellated bodies inmalarial blood.", Brit. Med. J., Dec. 8 (1894).

23. Sacharoff, "Über die selbständige Bewegung der Chromosomen bei Malaria Parasi-ten." Zentr. Bakteriol., (1895).

24. Ross, "Observations on the crescent-sphere flagella metamorphosis of the malarialparasite within the mosquito.", Trans. South Indian Branch, Brit. Med. Assoc., Dec.(1895). Also Indian Lancet, (1896) 227, 259.

25. Ross, "Observations on malaria parasites made in Secunderabad, Deccan.", Brit.Med. J., Feb. 1, (1896).

26. Manson, "The life-history of the malaria germ outside the human body.", Brit. Med.J., Mar. 15, 21, 28 (1896).

27. Ross, "Some practical points respecting the malarial parasite.", Indian Med. Gaz.,(1896) 42.

28. Ross, "Dr. Manson’s mosquito malaria theory.", Indian Med. Gaz., (1896) 264.29. Bignami, "Ipotesi dei parassitti malarici fuori dell’ uomo.", Policlinico, Jul. 15 (1896).

Also English translation in Lancet, 2 (1896) 1363, 1441.30. Ross, "Some experiments in the production of malarial fever by means of the mos-

quito.", Trans. South Indian Branch, Brit. Med. Assoc ., Dec. (1896). (Read Oct. 30,1896). Also Indian Med. Gaz.

3 1. Ficalbi, Revisione systematica d. fam. delle Culicidae Europea, Florence, 1896.32. Ross, "Observations on a condition necessary to the transformation of the malaria

crescent.", Brit. Med. J., Jan. 30 (1897) 251.3 3. Ross, "Further observations on the transformation of crescents.", Trans. South Indian

Branch, Brit. Med. Assoc ., Jul. (1897). (Read Jan. 29, 1897). Also Indian Med. Gaz.,Jan.(1898).

34. Ross, "Notes on some cases of malaria, Amoeba coli and Cercomonas.", Indian Med.Gaz., May (1897). (Proofs not corrected; full of typographical errors.)

35. Simond, "L’évolution des Sporozoaires du genre Coccidium.", Ann. Inst. Pasteur, Jul.(1897).

36. MacCallum, "On the flagellated form of the malaria parasite.", Lancet, Nov. 13(1897). Also J. Exptl. Med., 3 (1898).


37. Manson, "A method of staining the malarial flagellate organism.", Brit. Med. J., 2(1897) 68.

38. Ross, "On some peculiar pigmented cells found in two mosquitoes fed on malarialblood.", Brit. Med. J., Dec. 18 (1897) 1786.

39. Ross, "Pigmented cells in mosquitoes.", Brit. Med. J., Feb. 26 (1898).40. Ross, "Report on a preliminary investigation into malaria in the Sigur Ghat, Ootaca-

mund.", Trans. South Indian Branch, Brit. Med. Assoc., Feb. (1898). Also Indian Med.Gaz., Apr. (1898).

41. Manson, "Surgeon Major Ronald Ross’s recent investigations on the mosquito ma-laria theory.", Brit. Med. J., Jun. 18 (1898).

42. Ross, Report on the Cultivation of Proteosoma, Labbi, in Grey Mosquitoes, dated May21, 1898, Government Printing, Calcutta, 1898, p. 14. Also Indian Med. Gaz., Nov.,Dec. (1898). (In this copy only one of the plates is given.) Second edition, Govern-ment Printing, 1901. (Many printers’ errors.)

43. Manson, "The mosquito and the malaria parasite.", Brit. Med. J., Sep. 24 (1898).(Read at the Edinburgh Meeting of the British Medical Association at the end ofJuly.)

44. Grassi, "Rapporte tra la malaria e pecuhare insetti (zanzaroni e zanzare palustri)",dated September 29, Policlinico, Oct. 1 (1898).

45. Grassi, The same article as the above with the omission of certain passages, and un-dated, Atti Accad. Lincei - "pervenute all’Accademia prima del 2 Ottobre 1898".

46. Ross, Preliminary Report on the Infection of Birds with Proteosoma by the Bites of Mosqui-toes, dated Oct. 11, 1898. Government Press, Calcutta.

47. Grassi, "La malaria propagata per mezzo de peculiari insetti.", Atti Accad. Lincei, Se-duta del 6 Novembre 1898.

48. Bignami, "Come si prendone le febri malariche.", Ric. Sper., Bull. Accad. Med. Roma,dated Nov. 15, 1898. Also translation in Lancet, Dec. 3, 10 (1898).

49. Grassi and Dionisi, "Il ciclo evolutivo degli emosporidi.", Atti Accad. Lincei, sedutadel 4 Decembre 1898.

50. Bignami and Bastianelli, "On the structure of the semilunar and flagellate bodies ofmalarial fevers.", Lancet, Dec. 17 (1898).

51. Bastianelli, Bignami, and Grassi, "Kultivazione della semilune malariche dell’uomonell’ Anopheles claviger. Fabr.", Atti Accad. Lincei, inviata il 28 Novembre 1898; sedu-ta del 4 decembre 1898, p. 314.

52. Grassi, "Rapporte tra la malaria e gli artropodi.", Atti Accad. Lincei, seduta del 4 de-cembre 1898.

53. Bastianelli, Bignami, and Grassi, "Ulteriori ricerche sul ciclo parassiti malarici umaninel corpo del zanzarone.", Atti Accad. Lincei, dated Dec. 22, 1898. Also later papersread on Feb. 5 and May 7.

54. Ross, "Du rôle des moustiques dans le paludisme.", Ann. Inst. Pasteur, (1899) 136.Presented to the Académie de Médecine, Jan. 24, 1899.

55. Ross, "Extermination of malaria.", Indian Med. Gaz., Jul. (1899). (Report to GoV-ernment of India, dated Feb. 16, 1899.)

56. Bastianelli and Bignami, "Sullo sviluppo dei parassiti della terzana.", Bull Accad.

108 1 9 0 2 R . R O S S

Med. Roma, 1898-1899, Fasc. III dated Apr. 19. Also (with aggiunta), Ann. IgieneSper. (1899).

57. Grassi, "Ancora sulla malaria.", Atti Accad. Lincei, seduta del 18 giugno.58. Ross, "The possibility of extirpating malaria from certain localities by a new meth-

od.", Brit. Med. J., July 1 (1899).59. Ross, "Life-history of the parasites of malaria.", Nature, Aug. 3 (1899).60. Correspondent (R. Ross). "The malaria expedition to Sierra Leone.", Brit. Med. J.

Sep. 9, 16, 30, Oct. 14 (1899).61. Bastianelli and Bignami, "Sulla struttura dei parassitti malarici, e, in specie, dei ga-

mete dei parassite estivo-autunnale.", Ann. Igiene Sper., (1899).62. Grassi, Bignami, and Bastianelli, "Ciclo evolutivo delle semilune nell’ Anopheles cla-

viger ed altri studi sulla malaria dall’ Ottobre 1898 all Maggio 1899.", Ann. IgieneSper., (1899).

63. Koch, "Über die Entwickelung der Malaria Parasiten.", Z. Hyg. Infektionskrankh., 32(1899).

64. Koch, "Berichte über die Thätigkeit der Malaria Expeditionen.", Deut. Med. Woch-schr., (1899), (1900).

65. Nuttall, "On the rôle of insects, arachnids and myriapods, as carriers in the spread ofbacterial and parasitic diseases of man and animals.", Johns Hopkins Hosp. Rept., 8.Also in Hyg. Rundschau, (1899).

66. Nuttall, "Die Mosquito Malaria Theorie.", Zentr. Bakteriol., (1899).67. Ross, Annett, and Austen, Report of the Malaria Expedition of the Liverpool School of

Tropical Medicine and Medical Parasitology, Univ. Press Liverpool, Mem. 2, Feb., 1900.68. Ross, "Malaria and mosquitoes.", Nature, Mar. 29 (1900). Also French transl., Rev.

Sci., Jun. 23 (1900).69. Grassi, "Studi di uno zoologo sulla malaria.", Atti Accad. Lincei, 4 Giugno (1900).70. Lord Lister, Presidential Address to the Royal Society on the 30th November, 1900. EX-

tract in Brit. Med. J., Dec. 8 ( 1900).71. Daniels, Stephens, and Christophers, Reports to the Malaria Committee of the Royal

Society 1899-l903 (numerous papers).72. Ross, "Le scoperte del Prof. Grassi sulla malaria." (two papers), Policlinico, (1900),

(1901).73. Calandruccio, Le Scoperte del Prof G. B. Grassi Sulla Malaria, con note ed aggiunte. Tip

Barbagallo, Catania, 1900.74. Nuttah, "On the question of priority with regard to certain discoveries upon the

aetiology of malarial diseases", Quart. J. Microscop. Sci., (1901) 429.75. Theobald, A Monograph of the Culicidae or Mosquitoes, London, 1901.76. Ross, "Die Entdeckungen des Herm G. B. Grassi bezüglich der Malaria und der Mos-

quitoes", Deut. Med. Wochschr., Mar. 27 (1902) 231.77. Giles, Report on Kala-Azar, Assam Secretarial Press, 1890.78. Rogers, Report on Kala-Azar, Assam Secretarial Press, 1897. Also see Indian Med.

Gaz., Nov. (1897).79. Ross, Report on Kala-Azar, dated Jan. 30, 1899, Government Press, Calcutta, 1899.


Plates

These Plates are copied from those given in my Report on the Cultivation of Proteosoma,Labbé, in Grey Mosquitoes, dated the 21st May, 1898; but in the description I have sub-stituted for the appellation proteosoma-coccidia, temporarily used by me for the pigmentedcells , the word now generally employed, namely zygotes.

Note. All the figures and plates were drawn by me accurately according to scale fromactual preparations, most of which were preserved in formalin. Plates II to IX are faithfulrepresentations of entire fields.

110 1 9 0 2 R . R O S S

R E S E A R C H E S O N M A L A R I A

Plates II-VIII. Fields of Leitz oel. imm. 170 minim. 1/12 th (inch).

I I I

Plate II. External coat of stomach studded with young zygotes of about 30 hours. Airvessel, crossing muscular fibres, and some oil globules, are seen.

Plate I. Drawings of zygotes from the second to the twelfth day.

Figs. 1-5, zygotes of the second day. Fig. 6, stained.Figs. 7-11, zygotes of the third day. Fig. 12, stained.Figs. 13, 14, 15, zygotes of the fourth day. Fig. 16, stained.Figs. 17, zygote of the fifth day.Figs. 18-22, zygotes of the sixth day and later.Figs. 23, drawing in outline of the stomach of a mosquito studded with zygotes of the

sixth day, seen by a low power.

1 1 2 1 9 0 2 R . R O S S

Plate III. External coat of stomach studded with young zygotes of about 40 hours.


Plate IV. Zygotes of third day. Vacuolated forms.

114 1 9 0 2 R . R O S S


Plate VII. Zygotes of the fifth day.

116 1 9 0 2 R . R O S S

Plate IX. Pyloric end of stomach studded with zygotes of the seventh day, seen by apower of medium strength.

researches on malaria - nobelprize.org · 2020-02-05 · researches on malaria 29 which cause...

Documents